Crime Scene Training

UK Scientists make revolutionary forensic science breakthrough

2013-10-30T13:56:17-04:00

A team of North-East scientists have made a breakthrough which is expected to revolutionize forensic science.

Researchers at Teesside University have developed a way of detecting minute blood stains which would not be seen using current technology.

They have also found a way of checking the age of blood stains - something which is regarded as a holy grail of forensic science.

The failure to locate traces of blood during the original forensic examinations meant that the killers of both Stephen Lawrence and Damilola Taylor evaded justice.

It was only years later that traces of blood were identified and the killers were eventually brought to justice.

Experts hope the new blood detection technique will help investigators avoid these mistakes in the future.

It works by using a technique known as visible wavelength hyperspectral imaging.

This allows for the positive identification of blood which may be confused with other red colored substances.

It also enables investigators to pinpoint the age of a one month old blood stain to within one day.

Chemist Dr Meez Islam, see accompanying photo, who is one of the academics behind the forensic breakthrough, which also involved his colleagues Liam O'Hare, Peter Beveridge and PhD student Bo Li, said: "Often you go to crime scenes and what appears to be blood isn't blood.

"Blood on dark backgrounds can be hard to see and there are traces of blood that are not visible to the naked eye.

"We have developed a technique which is a non-contact, non-destructive way of detecting and identifying blood.

"We use a camera with a liquid crystal tunable filter which takes a series of pictures at different wavelength bands and can identify blood stains through its unique absorption spectrum.

"It can quickly differentiate between what is blood and what isn't and it can locate blood stains on problematic areas such as red clothing or dark backgrounds and at diluted amounts.

"What this does is provide fast, at the scene identification of blood and speeds up the investigative process as items do not need to go back to a laboratory to be examined."

Dr Islam and his team currently have a prototype instrument and are in talks with manufacturers about developing a commercial instrument.

"Current methods for age determination of blood stains are neither accurate, reliable, robust nor usable at a crime scene," said Dr. Islam, who said the development was potentially "a huge step forward" for forensic science.

To mark the 21st anniversary of forensics at Teesside - which was the first university to offer crime scene courses - a special celebratory event is taking place at the university on Thursday, November 7.

Bestselling crime writer Val McDermid, famous for her Wire in the Blood series, will be the guest of honour and will talk about how scientific fact is now informing fiction.

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Enhancing of Blood Prints on Washed Clothing Using Luminol and LCV Reagents

2013-08-06T07:53:12-04:00

Thomas W. Adair and Rebecca L. Shaw

Introduction:

Luminol and LCV are commonly used reagents to develop latent bloodstains on evidence and at crime scenes. Luminol was first used to detect latent bloodstains in 1937 (1). Since that time the use of luminol has become very popular with many law enforcement agencies. The application of luminol creates a blue/green color chemiluminescence from its reaction with hemoglobin. Observation and subsequent documentation of latent bloodstain reactions with luminol require near to total darkness for best results. Leuco-crystal Violet (LCV) is another commonly used latent blood reagent for evidence and crime scenes. Bodziak (2) reports that the Federal Bureau of Investigation laboratory has utilized LCV since 1993. Like luminol, the application of LCV to latent bloodstains creates a catalytic reaction with hemoglobin. Unlike luminol, however, the LCV reaction is visible in normal lighting. LCV stains latent blood a dark purple to black color allowing for easy observation and documentation on light colored surfaces. Bodziak does caution that visible bloodstains on fabric are best processed with DAB or Amido Black reagents.

This research investigates the use of luminol and LCV to develop latent bloodstains from clothing, which has been washed with a commonly available cleaning product. A second aspect of this research was to test the use of the phenolphthalein as a presumptive blood test on the washed clothing items. A search of the major English language forensic journals and textbooks relating to bloodstain pattern analysis did not reveal any study that specifically examined the use of reagents on washed clothing. Quickenden et. al. (3) conducted research on the effectiveness of luminol in detecting washed bloodstains from automobile interiors. One interesting observation of their experiments was the conversion of hemoglobin to methemoglobin from increased heat in the motor vehicle following the deposition of blood. This resulted in and increased (enhanced) sensitivity of the luminol reaction. Not surprisingly, the authors discovered that repeated washings of interior surfaces decreased the sensitivity of the luminol reaction compared to non-washed surfaces. The authors did note, however, that the cleaning of carpet with a water and soap solution removed only the surface staining, leaving a strong presence within the foam padding of carpeting. Large quantitative differences in luminol reaction were observed between various carpet styles and commercial cleaning solutions however. Creamer et. al. (4) conducted research to determine the effect of the luminol reaction following the use of a known interfering catalyst (bleach) on washed items. The authors noted that luminol is highly sensitive, capable of detecting nanogram traces of blood. While their experiments were conducted on nonporous ceramic tiles, they observed that interference from bleach dissipated after approximately eight hours. DeHaan et. al. (5) also conducted sensitivity experiments with LCV on both porous and non-porous surfaces. Their research indicated LCV could detect blood at a dilution of 1:10,000, considerably less than luminol.

Gifford (6) reported a case study in which bloodstains were found on the clothing of a male victim who had been discovered in water six days following his death. The author conducted experiments on bloodstained clothing in moving and stagnant water and found that bloodstains would not remain on the clothing after 30 minutes in moving water and not more than three hours in stagnant water. Certainly the action of the washing machine will dissipate blood at an even faster rate. Following his experiments, Gifford concluded that diffused blood still visible on the victim’s wet or washed clothing was deposited after the clothing was removed from the water source (in that case a stream).

Materials and Testing Methods:

All experiments were conducted at the Arapahoe County Sheriff’s Office Crime Laboratory in Centennial, Colorado in July of 2005. Whole horse blood obtained from a local veterinarian hospital was used for all experiments. Quickenden and Cooper (7) experimented with the luminol reaction using both human and bovine hemoglobin and found no significant difference in luminol reactions. Ten white colored Haynes brand “signature collection” 100% cotton undershirts were used for these experiments. The shirts had been worn for approximately 6-8 months prior to experimentation but had not previously been stained with blood. There was no visible discoloration or staining in the testing areas prior to the experiments. An eleventh shirt of the same condition was used as a control. The shirts were labeled #1-11 near the neckline with a black Sharpie brand marker (designations “B” and “F” for back and front). Three different types of bloodstain patterns were produced on both the front and back of each shirt (Figure 1).

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Blood Stain Terminology

2012-07-25T12:50:19-04:00

FBI Forensic Science Communications

Scientific Working Group on Bloodstain Pattern Analysis (SWGSTAIN)

Objective

This document provides a recommended list of terms to use when teaching, discussing, writing, or testifying on bloodstain pattern analysis.

Introduction

The Scientific Working Group on Bloodstain Pattern Analysis (SWGSTAIN) comprises bloodstain pattern analysis (BPA) experts from North America, Europe, New Zealand, and Australia. SWGSTAIN provides a professional forum in which practitioners in BPA and related fields can discuss and evaluate methods, techniques, protocols, quality assurance, education, and research. SWGSTAIN’s ultimate goal is to use these professional exchanges to address substantive and operational issues within the field of BPA and to build consensus-based, or “best practice,” guidelines for the enhancement of the discipline of BPA.

Statement of Purpose

SWGSTAIN has developed and defined a list of recommended terminology for use in BPA. In developing this list, SWGSTAIN reviewed terminology in use across BPA.

Recommended Terminology

Accompanying Drop

A small blood drop produced as a by-product of drop formation.

Altered Stain

A bloodstain with characteristics that indicate a physical change has occurred.

Angle of Impact

The acute angle (alpha), relative to the plane of a target, at which a blood drop strikes the target.

Area of Convergence

The area containing the intersections generated by lines drawn through the long axes of individual stains that indicates in two dimensions the location of the blood source.

Area of Origin

The three-dimensional location from which spatter originated.

Backspatter Pattern

A bloodstain pattern resulting from blood drops that traveled in the opposite direction of the external force applied; associated with an entrance wound created by a projectile.

Blood clot

A gelatinous mass formed by a complex mechanism involving red blood cells, fibrinogen, platelets, and other clotting factors.

Bloodstain

A deposit of blood on a surface.

Bloodstain pattern

A grouping or distribution of bloodstains that indicates through regular or repetitive form, order, or arrangement the manner in which the pattern was deposited.

Bubble Ring

An outline within a bloodstain resulting from air in the blood.

Cast-off Pattern

A bloodstain pattern resulting from blood drops released from an object due to its motion.

Cessation Cast-off Pattern

A bloodstain pattern resulting from blood drops released from an object due to its rapid deceleration.

Directionality

The characteristic of a bloodstain that indicates the direction blood was moving at the time of deposition.

Directional Angle

The angle (gamma) between the long axis of a spatter staintarget. and a defined reference line on the

Drip Pattern

A bloodstain pattern resulting from a liquid that dripped into another liquid, at least one of which was blood.

Drip Stain

A bloodstain resulting from a falling drop that formed due to gravity.

Drip Trail

A bloodstain pattern resulting from the movement of a source of drip stains between two points.

Edge Characteristic

A physical feature of the periphery of a bloodstain.

Expiration Pattern

A bloodstain pattern resulting from blood forced by airflow out of the nose, mouth, or a wound.

Flow Pattern

A bloodstain pattern resulting from the movement of a volume of blood on a surface due to gravity or movement of the target.

Forward Spatter Pattern

A bloodstain pattern resulting from blood drops that traveled in the same direction as the impact force.

Impact Pattern

A bloodstain pattern resulting from an object striking liquid blood.

Insect Stain

A bloodstain resulting from insect activity.

Mist Pattern

A bloodstain pattern resulting from blood reduced to a spray of micro-drops as a result of the force applied.

Parent Stain

A bloodstain from which a satellite stain originated.

Perimeter Stain

An altered stain that consists of the peripheral characteristics of the original stain.

Pool

A bloodstain resulting from an accumulation of liquid blood on a surface.

Projected Pattern

A bloodstain pattern resulting from the ejection of a volume of blood under pressure.

Satellite Stain

A smaller bloodstain that originated during the formation of the parent stain as a result of blood impacting a surface.

Saturation Stain

A bloodstain resulting from the accumulation of liquid blood in an absorbent material.

Serum Stain

The stain resulting from the liquid portion of blood (serum) that separates during coagulation.

Spatter Stain

A bloodstain resulting from a blood drop dispersed through the air due to an external force applied to a source of liquid blood.

Splash Pattern

A bloodstain pattern resulting from a volume of liquid blood that falls or spills onto a surface.

Swipe Pattern

A bloodstain pattern resulting from the transfer of blood from a blood-bearing surface onto another surface, with characteristics that indicate relative motion between the two surfaces.

Target

A surface onto which blood has been deposited.

Transfer Stain

A bloodstain resulting from contact between a blood-bearing surface and another surface.

Void

An absence of blood in an otherwise continuous bloodstain or bloodstain pattern.

Wipe Pattern

An altered bloodstain pattern resulting from an object moving through a preexisting wet bloodstain.

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Detecting Blood Evidence After Bleaching

2011-08-10T08:22:33-04:00

Bleach Used to Cleanp Up Crime Scenes

ExploreForensics: http://www.exploreforensics.co.uk/

Most people know that forensics involves many different kinds of evidence, whether that is blood evidence or a weapon. However, the evidence can become degraded from a number of things such as time, heat or the use of bleach. Unfortunately, even advanced forensic techniques can be challenged by the use of a common kind of bleach found in many homes.

Understanding Bleach And Evidence

To understand how it all works, you have to consider that there are two kinds of bleach that are found in the majority of cleaning products within your home. There are bleaches that are primarily chlorine and there is also oxygen bleach.

Chlorine bleaches can remove a bloodstain to the naked eye but fortunately, forensics experts can use the application of substances such as luminol or phenolphthalein to show that hemoglobin is present. In fact, even if the shady criminal washed a bloodstained item of clothing 10 times, these chemicals could still reveal blood.

With oxygen bleach, the bleach has an oxidising agent, which could be a substance such as hydrogen peroxide. In these instances, hemoglobin is completely removed and can't later be detected. As expected, this presents a unique challenge for forensic scientists. Not only that, but it can significantly compromise an investigation and may mean thatevidence is not properly investigated and used in a trial.

Testing Out Bleaches

To properly assess whether bleach could fully remove blood, researchers soaked some bloodstained clothing in oxygen bleach for a couple of hours. After the bleaching, stains did look faded, although they were still somewhat noticeable. On the other hand, even though there was some visible marking, luminol and phenolphthalein didn't detect the haemoglobin on the clothing.

Challenges Of Detecting Bleach

The results are worrying because a stain on clothing could be assumed to occur from something else when a test shows up negative for hemoglobin. Eventually, valuable evidence could ultimately be dismissed, which then affects the entire criminal investigation and trial proceedings.

Forensics experts will not examine and check for important DNA evidence until they have initially found an appropriately identified blood sample. In this way, the entire investigation is compromised and the opportunity to obtain more information is lost.

Fortunately, there is a better chance of obtaining useful information from the seams of clothing. While washing does remove a great deal of evidence in the rest of the garment, it is far more challenging for a criminal to remove evidence found in the clothing seams.

Improving Forensic Science

The study is an important one that highlights the limitations and scope of forensics techniques in science today. Clearly, we have many advanced and sophisticated tools to investigate blood evidence.

Yet, science can't always compete with materials used to remove these stains, such as oxygen bleach. However, it is at least a positive step that we can identify these challenges, which means that efforts can be focused on finding ways to overcome them and identify blood even after all kinds of bleaching. In the end, this is good news for forensics but bad news for criminals.

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Written in Blood--Messages Crime Scene Investigators Find in Blood Spatter

2011-07-25T07:54:58-04:00

Blood Spatter Holds a Message for CSIs

By: Don Penven

Youngsville, NC

In the novel and later the motion picture, “The DaVinci Code,” a Harvard symbologist teams up with a French police cryptologist. The gist of the opening storyline is that the symbologist is called to a murder scene at the Louvre Museum since a note containing the name of this fellow was found on a murder victim. As the story progresses, he meets a young woman cryptologist with the French police, who is the granddaughter of the victim. The two are left alone in the crime scene for a few minutes and they find an Ultra Violet light left behind by crime scene investigators.

Using this UV light, they discover a message that glows under the light beam, written in blood on the museum floor. The message was to the granddaughter. Later the two find a second message written on the back of a painting—The Mona Lisa.

The entire storyline was based on the fluorescence of the nearly invisible blood. But the fact is that in reality—blood does not fluoresce! Yes, that’s how Hollywood depicts crime scene investigation on TV and the Silver Screen. And to perpetuate the illusion, because UV light is invisible, they use a blue (visible) light source to simulate UV.

Blood will—on the other hand—luminesce, that is, it actually is emitting light energy when a chemical like Luminol, BlueStar, Hemiscene or Lumiscene is sprayed on it. So much for Hollywood reality!

Blood spatter (often mistakenly called blood splatter) at the crime scene is a very valuable form of physical evidence. And blood stains can tell quite a story about what actually happened at the scene. Of course many crime scenes have visible blood spattered all over floors, walls and even ceilings. This visible blood poses no collection problems, and the CSI will collect samples from pooled blood as well as the spatter resulting from a blood-drenched knife or baseball bat being swung through the air as repeated strikes are inflicted upon the victim.

It is very important that blood evidence be properly documented and crime scene photos should include the following:

1. Medium wide angle shot of the area

2. Close up with a scale and with surrounding objects included

3. Detailed: Close enough to record direction of travel of blood spatters, with a scale included

In many crime scenes, the perpetrator makes an effort to “clean-up the area,” but rarely do they perform a thorough job of it. Blood on carpet or rugs is easily cleaned off the surface with soap and water. But the underside usually has some residue on it, and the blood may have seeped through to the floor under the carpet.

Even mopping up blood from solid surfaces like tile or wood floors may leave traces—invisible to the naked eye. This is where the CSI employs the chemical reagents that produce luminescence mentioned above.

Sometimes the search yields what is suspected to be blood but confirmation is needed. It may be very obvious to the investigator that the material he observes is blood. But he does have the tools to confirm his hunch to a degree. Two reagents are popular means of determining the “probable, presumptive” presence of blood: Phenolphthalein and Leucomalachite Green.

The crime scene offers grim testimony to what transpired in that place. And the viciousness of the attack is easily discerned by the amount and spread of the victim’s blood. Enter the Blood Spatter Analyst (also referred to as Blood Pattern Analysts, (International Association of Blood Pattern Analysts [IABPA]).

The study of how and why blood is strewn about a crime scene is left to a recently developed breed of crime scene investigators—blood spatter analysts. But is this specialty really needed, and if so—why?

The ancient term, “Blood is thicker than water,” is a truism, because, in fact, blood really has a greater density. For want of a better example, fresh blood has the consistency of the Half and Half we use in our coffee.

When blood drips from a wound onto the floor or is flung through the air when it breaks free of a weapon or a bullet passes through the body, the blood’s trajectory and travel are predictable. And the stains that are left behind can paint a vivid picture of the crime in progress. Blood spatters are words from the grave.

Several factors influence how blood travels on a surface or through the air and how it behaves when it strikes a surface. These factors include gravity, friction and surface tension of liquids. When a drop of blood falls free into the air, during its downward travel it begins with a tear drop shape. But with gravity tugging it down while surface tension holds it together and friction from the air surrounding it, the drop turns it into a perfect sphere until it contacts the surface.

The surface tension struggles to keep the sphere in its round shape but momentum and gravity cause the surface tension to release its grip and it spatters onto the surface. If the drop hits the surface at a straight-down 90-degree angle it leaves a round stain. If it strikes the surface at an angle, the stain becomes elongated. Elongated blood stains can be used to determine, within inches, where they originated from.

And this is what blood spatter analysis is all about. In other articles of this series, you will learn how analysts determine where the victim was when struck or shot and where the perpetrator was positioned.

If this article has aroused your curiosity about blood spatter analysis or crime scene investigation in general, you are invited to download a publication that includes a wealth of training material as well as full descriptions and photographs of the equipment and materials used by real-life CSIs and those depicted on TV and in the movies. CLICK HERE for access to the website.

Download a FREE copy of the “Evidence Collection Mission.”

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Blood Spatter Training From U of WA

2011-03-28T10:58:29-04:00

The University of Western Australia offers a comprehensive program in Forensics. Using special permission, we are pleased to provide links to some of their outstanding training material on “Blood Spatter.”

What is Forensic Science: This document offers a good perspective overview of a topic of interest to all CSIs. What Is Forensic Science

All About Blood: Blood is a fluid that makes up approximately eight percent of the total weight of humans. This equates to between four and five litres in females and between five and six litres in males. All About Blood

Properties of Blood: Learn about blood viscosity, surface tension, density, blood droplets and more… Properties of Blood

Latent Blood Prints – Methods For Chemical Enhancement

2011-03-16T08:17:15-04:00

Blood is often found on various surfaces at crime scenes where physical violence occurred. Therefore, blood acts as a transfer medium for latent fingerprints and shoeprints. On some occasions the blood residue retains enough color and detail to permit direct photographic recovery, but generally the blood marks are too faint to permit photography using conventional light sources.

In a report published by the California Department of Justice, Bureau of Forensic Services. scientists conducted significant research indicating that certain reagents may be introduced to the visible stains or areas suspected of containing latent blood impressions.

For many years, forensic scientists have used reagents such as Leucomalachite or Ninhydrin to develop blood stains, but both of these substances have a tendency to run off or distort the prints on non-porous surfaces. On the other hand, Amido Black has proven to be quite useful.

This article reviews three popular methods for blood print enhancement: Amido Black, Leuco Crystal Violet (LCV) and Hungarian Red

Amido Black

Amido black is very sensitive and works well on non-porous surfaces but its high background color (light to medium blue) compromises contrast on multi-colored porous surfaces.

Amido Black is a protein stain, and as such should not be considered as even a presumptive test for blood, let alone a confirmatory test. The protein may be present in other body fluids, in addition to blood. However, other actual presumptive tests may be successful after the application of amido black.

The Amido Black staining solution can be methanol—or water-based. Amido Black in methanol has a greater staining power, but due to the toxicity of the methanol, it is also more dangerous. For use on a crime scene (for example, shoeprints in blood) the water-based staining solution is advised.

Amido Black Aqueous Solutions—Field or Lab Use

To Create an Aqueous Fixing Solution—Solution No. 1 (makes 1000ml):

1. Weigh out 20g of 5-Sulphosalicylic Acid. Place in a clean, dry, 2 liter glass beaker.

2. Measure out 1-liter of Distilled Water. Add to the 5-Sulphosalicylic Acid while stirring with a magnetic stirrer.

A clear water-based Fixing Solution will be produced

3. Transfer the water-based Fixing Solution to a clean, dry, labeled, 1 liter plastic coated glass bottle equipped with a tightly fitting screw cap. (Unused water-based Fixing Solution will keep indefinitely.)

To Create An Aqueous Working Solution—Solution No. 2 (makes 1000ml):

1. Weigh out 2g of Amido Black. Place in a clean, dry, 2 liter glass beaker.

2. Weigh out 20g of citric acid. Add to the Amido Black.

3. Measure out 1 liter of distilled water. Add to the beaker. Stir with a magnetic stirrer for at least 30 minutes. A blue-black working solution will be produced.

4. Transfer the water-based Working Solution to a clean, dry, labeled 1 liter plastic coated, glass bottle with a tightly fitting screw cap. (Unused water-based Working Solution will keep indefinitely.)

Amido Black Application Procedure:

Aqueous Solutions

Note: The fixing and working solutions may be applied using a spray application. For tray development follow the procedure below:

Photographs of any visible prints must be taken before proceeding. Important Note : Before using this technique on a corpse, clear the procedure with the Coroner’s or Medical Examiner’s Office.

1. Pour sufficient water-based fixing solution to treat the article into a clean, dry, metal dish or pan.

2. Immerse the article in the fixing solution for five to six minutes. Longer times may be needed to fix heavy blood deposits. Beware of cross-contamination of DNA evidence if more than one article is processed. Discard the water-based fixing solution.

3. Pour sufficient water-based working solution into a clean, dry, metal dish or pan to treat the article. Pour a similar volume of distilled water into two other containers. If the article cannot be fully immersed, apply the working solution and distilled water using a wash bottle above the prints, and allow the solutions to run down over the prints.

4. Immerse the article in the working solution for three to four minutes. Working solution may be replenished as needed. Discard used working solution when complete.

5. Immerse the article in distilled water. Rock the dish gently until excess dye has been removed from the background and greatest contrast is achieved between the prints and the background.

6. Allow the article to dry at room temperature.

7. Photograph useful prints.

Staining can be cleaned using a solution of 10% bleach.

You may download a copy of the complete Amido Black Technical Bulletin Here:

Amido Black Latent Print

Leuco Crystal Violet

This reagent does not react to the normal finger constituents found in latent fingerprints like eccrine or sebaceous deposits. Rather, this reagent has an affinity for heme-based materials. When LCV and hydrogen peroxide come into contact with the hemoglobin in blood, a catalytic reaction occurs and a blue to purple/violet reaction product occurs. Leuco Crystal Violet may be used on both porous and non-porous surfaces, and may be applied with a fine mist spray or by immersing an object in the solution.

A number of sources offer LCV in kit-form, with pre-packaged and pre-measured reagents. To download the complete technical Information Bulletin: Click This Link To Technical Information

LCV Shoeprint on tile floor

Hungarian Red

Hungarian Red was developed through a cooperative effort of the police forces in Hungary and Holland. The intent was to create a formula that would be highly sensitive to blood residue, and subsequent testing has indicated that Hungarian Red may be more sensitive than other processes such as Amido Black.

Hungarian Red is an aqueous solution for staining impressions found in blood. It is much safer than other staining compounds due to its water-based formula. It has been used in actual crime scenes to recover nearly invisible latent fingerprints and footprints in blood. NOTE: As with similar chemicals, collect all DNA evidence from the crime scene before using Hungarian Red because this process will interfere with subsequent blood analysis. Do not use Hungarian Red on handwriting samples, inks, hairs, fibers, and other physiological fluids that will be subsequently subjected to other forms of forensic examination.

Hungarian Red may be used on most porous and non-porous surfaces.

Lifted traces and weak traces on dark or confusing backgrounds fluoresce under a green alternate

light source (520nm-560nm) such as the, MMX100 megaMAXX™ and MMX300 megaMAXX™ III. Once fluoresced, view and photograph the evidence with orange or red barrier filters.

PROCEDURE

Hungarian Red is supplied in sprayer containers. Place small objects in a suitable tray and spray the reagent onto the object from a distance of 6"-9" (15.2cm-22.9cm). Allow about one minute for the dye

to set. Then, wash lightly with water or a water/acetic acid mixture. Remove any remaining water

droplets with compressed air or a hair dryer set on low heat. The surface must be completely dry before attempting to lift the developed prints using gelatin-type lifters. When examining larger objects, apply the reagent directly to the surface.

You may download a complete copy of the Technical Information Bulletin

The left side of this image shows visible red staining from Hungarian Red. It fluoresces when excited with 520-560nm (right).

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How Police Find Latent Blood Prints

2011-03-14T15:41:46-04:00

Latent fingerprints, as described in earlier articles in this series, are fingerprints left at a crime scene that are not readily visible to the naked eye. But some crime scenes, especially those where physical violence has occurred, may harbor latent blood fingerprints and foot prints as well.

Identifying Stains

The first step is to determine if the visible stains are probably blood. The tests most often employed by CSIs are either Phenolphthalein or Leucomalachite. Keep in mind, however, that some reagents will interfere with subsequent blood typing or DNA analysis—so samples must be collected first.

Phenolphthalein is considered to be the most sensitive (1:10,000) and is recommended for testing small droplets or smears. This reagent produces a pink stain, which is presumptive of the presence of human blood.

Leucomalachite can be used on larger concentrations of blood and it produces a green/blue stain, but it is not as sensitive as phenolphthalein.

Use the contact method of testing with these two reagents, transferring blood from the suspect stain to a cotton swatch saturated with distilled water for testing, rather than applying the reagent directly to the stain.

Presumptive Blood Identification Procedure

Phenolphthalein and Leucomalachite application principles are identical. These two reagents are supplied in disposable chemical applicators (DISCHAPS) or in glass ampoules.

Photo Ampoules:

If the possibility exists that blood stains have been cleaned up, then examination of the area should be undertaken using reagents such as Luminol, Blue Star, Lumiscene, etc. These reagents produce a blue luminescence. Luminol may only be seen in total darkness while Blue Star and Lumiscene may be viewed under low light conditions

Searching For Latent Blood Prints

Latent foot prints occur when someone steps in blood as they navigate around the crime scene. With each step blood is deposited onto the surface. Many times these visible impressions show very little visible detail because of saturation, but later diluted steps, that are not visible to the eye, can reveal these details with astute processing. It isn’t until several steps are taken that these impressions become visible.

Several different chemical formulas are available to restore the latent foot print to visibility.

The same thing occurs when the person at the crime scene has blood on his fingertips and he leaves latent blood fingerprints as well.

Below are listed four different reagents that have been successful in producing visible blood prints in numerous crime scenes.

Leuco Crystal Violet is one of the most sensitive reagents and one of the most popular for use at crime scenes. Individual components are packaged in separate containers since the mixture becomes unstable after a short time. This reagent does not react to the normal finger constituents found in latent fingerprints like eccrine or sebaceous deposits. Rather, this reagent has an affinity for heme-based materials, such as hemoglobin in the blood. Developed latent blood prints are violet in color. This reagent may be sprayed on the surface or tray-development may be employed. This reagent works best on non-porous surfaces.

Coomassie Blue is another reagent that will enhance latent fingerprints and foot prints contaminated with blood on porous and non-porous surfaces. The working solution is sensitive to the proteins found in blood. If weak prints are observed after applying the reagent, the procedure may be repeated for maximum contrast. Latent blood prints will be blue in color.

Hungarian Red is a powdered dye but is available in premixed form. Hungarian Red is the outcome of an effort by police forces in Hungary and Holland. Researchers sought a formula that would be highly sensitive to blood residue, and subsequent testing here in the U.S. indicates that this reagent may be more sensitive than other methods such as Amido Black. Hungarian Red also has fluorescent properties and may be viewed with an alternate light source operating in the range of 520 to 560 nanometers.and is viewed with a red filter.

Amido Black is a biological dye that stains the protein present in blood and some other body fluids, producing a dark blue-black image. It is extremely useful in developing latent fingerprints contaminated with blood, but cannot be used on dark surfaces, as it will be hard to visualize the stain. Amido Black can be used on almost any surface, porous and non-porous; however, some porous surfaces will completely stain, hiding any detail of the prints. It can be used on the skin of corpses, but it should not be used on live skin. Be certain to check with the medical examiner/coroner prior to applying reagent to corpses.

Part 2. of this series will offer specific formulations for the reagents listed above. If you are interested in gaining more information on crime scene investigation, you are invited to download a free copy of the training manual, “The Evidence Collection Mission.” You may retrieve your copy by Clicking HERE. Evidence Collection Manual

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Blood Spatter: What Does it Tell The Blood Spatter Analyst

2010-12-08T16:15:18-05:00

The interpretation of blood spatter was first mentioned in a paper written in the 1890s by a researcher at the Institute for Forensic Medicine in Poland, Dr. Eduard Piotrowski. His work, "Concerning the Origin, Shape, Direction and Distribution of the Bloodstains Following Head Wounds Caused by Blows." But it took nearly 50 years before cases that included the interpretation of blood spatters appeared.

A significant number of high profile criminal cases have been prosecuted when blood spatter evidence was included among the physical evidence. One such case was the highly publicized trial of the State of Ohio v. Samuel Sheppard. In 1955, Dr. Paul Kirk offered an affidavit on blood spatter analysis, which was the earliest instance for the legal system to be made aware of the value of blood spatter analysis. Kirk’s analysis was able to show the location of the victim and the assailant, and it showed that the victim was struck by the assailant’s left hand.

Other cases involving prominent personalities where blood spatter entered into the evidence were the O.J. Simpson murder case and the trial of noted author, Michael Peterson of Durham, NC.

A leading authority in this field is Dr.Herbert MacDonell, who published in 1971, "Flight Characteristics of Human Blood and Stain Patterns." MacDonell has trained countless crime scene investigators in blood spatter analysis as well as training analysts.

The blood spatter analyst is seeking the following information from blood stain patterns.

1. Is it blood? This can be determined by simple, portable field tests using chemicals such as Phenolphthalein or Leucomalachite. These tests are presumptive in nature and are not proof positive that the substance is blood. But the likelihood is that the substance is probably blood and not tomato juice or paint. But these tests do not differentiate between human and animal blood, which require further laboratory analysis.

2. Trajectory of the blood droplets: Using visual examination at first, the analyst can tell whether a droplet struck the surface at a 90-degree angle or at some more acute angle. When a blood droplet strikes the surface at 90-degress it leaves a circular stain. If it travels into the surface from angle, the stain will be elongated—resembling an exclamation point with the narrow end of the stain pointing in the direction of travel—away from the source.

3. Using specific measurements of the actual size of the stain (length vs. width), it can determine the actual angle of travel to the surface using a trigonometric formula..

4. Once the angle of incidence is determined, the analyst attaches strings to the surface that simulate the flight path of these droplets. The strings will all cross each other at some distance from the surface and this indicates the point of origin of the various stains.

Using this method, the analyst can determine if the victim was standing or kneeling and how far away he was from the surface that contained the blood stains. For photographs that illustrate the above steps, see the article posted HERE.

To become a blood spatter analyst, specific training is required to reach the point that the analyst is accepted as an expert in this field. Additional articles on blood evidence will be posted on this site shortly. To learn more about how CSIs identify possible blood stains at the crime scene, download a free technical bulletin at the website listed below.

Blood Kit Technical Manual

Don Penven

Blood Spatter and Newton's Third Law

2010-12-08T15:56:02-05:00

Blood Spatter and Newton's Third Law

It's the little details that trip up the criminal every time.

Dr. Doug Hanson

DR. DOUG HANSON

dougmh@comcast.netdougmh@comcast.net

Forensics Contributor
Officer.com

Dr. Tom Harper thought he had committed the perfect crime. He had shot his wife in a manner that should have left the bullet hard to find and identify. Then he had repeatedly stabbed her dead body with a kitchen knife, and after wiping off any fingerprints, dropped the knife in their backyard. Nearby, he made several impressions in the soft dirt with a sneaker that was two sizes larger than his shoe size. The house had been ransacked, and jewelry and some other item were missing. It looked like the perfect setting for a random house invasion scenario.

Establishing an Alibi

Dr. Harper, the director of a large dental clinic, then left his house through the back woods and picked up his car, which was on an isolated road about a half mile away. One of the advantages of living way out in the country was in having no neighbors close by to see things they shouldn't. Harper proceeded to his office and went into a 9:00 am meeting with his staff. While he was committing this crime, he periodically went to his laptop and typed an e-mail to several people to establish that he was in his office all the time. To bolster his alibi, he sent the e-mails to his office computer using remote desktop software, and then forwarded them to the recipients. There would be no trace of the e-mails coming from his house.

Alice Harper was a large woman who worked out regularly at the gym. Tom Harper knew that he would never be able to stab her without her fighting back and leaving signs of a struggle. His plan was to shoot her in the back at close range with a small caliber .22 pistol. His knowledge of anatomy allowed him to shoot her in a way that would penetrate the abdominal aorta and cause her to immediately bleed out into her abdomen. Once on the floor, he would stab her repeatedly with a kitchen knife. Hopefully, at autopsy, they would only look at the stab wounds and not look for a small gunshot wound in her back. To ensure this, he also stabbed her in the back several times, including through the gunshot wound area.

The Problem

But this plan left a problem: the bullet. Surely the medical examiner would find the lead slug. He had looked into frangible .22 bullets, something like a CCI Quik-Shok, but they only fragmented into two or three pieces and the likelihood of one or more being found would be too great. This kind of bullet would also tear up some other organs, and he wanted this to be a clean shot into the aorta. When he stabbed her, he would be sure to hit the aorta first in the front, making it look like a knife wounds had ruptured it.

This problem plagued him until one day, as he was rebuilding a patient's broken tooth, he had a thought. What if he removed the bullet from the .22 shell and built up a bullet made of dental restorative composite, like Gradia or some other polymer material? If he made the material not too smooth on the surface, it would probably be overlooked as a bone fragment, and he could color the composite to match bone. On studying some literature, he found that by incorporating calcium phosphate gel into the composite when he made it, the bullet would be strong enough to penetrate the body, but then break into several pieces. Furthermore, if he stabbed her in the stomach, the hydrochloric stomach acid would leak out, and could dissolve the calcium gel, degrading the bullet fragment even further.

The Crime

Harper was convinced his scheme was foolproof. He prepared several bullets, then shot them into watermelons out in the woods, adjusting the polymers till he got the effect he wanted. He picked a Thursday morning to shoot her, knowing that her best friend would come at around 10:30 am to pick her up to go shopping. His last task was to break the window in the back door at the kitchen, the point of entry for the robber.

When her best friend called 911 reporting her dead, the local crime scene investigators and coroner soon arrived at the Harper residence. The coroner did a preliminary exam at the scene, and determined that the first knife wound had apparently penetrated the aorta. This would explain the lack of significant bleeding at the site of the other knife wounds.

Severing of the aorta caused her to bleed into the abdominal cavity so fast that her blood pressure fell, and blood was not readily supplied to the other wound areas. Tom, who was sitting nearby appearing to grieve over his wife's death, heard the coroner tell the investigators this. He mused to himself that they had bought it, so far.

The CSI team finished their work hours later, but found little physical or trace evidence to go on. The murder weapon was found on the lawn, but wiped clean of prints. They sent it to the lab to be superglue-fumed for latent prints. Cast of the large shoe prints in the soft dirt were made, and a variety of fibers and hairs were bagged, but they all would turn out to be either those of Alice, Tom, or their son Alec, who was away at college.

A Lingering Suspicion

Still, to investigators it looked a little too clean--a little too perfect. Knowing that the husband is always a potential suspect in homicides, Harper cooperated with the police in all interrogations. A co-worker who was interviewed mentioned that Harper had worn a red flannel shirt the day of the murder. On a hunch, the lead CSI asked Tom for the clothes he was wearing that day. Since Harper was right handed and also wore his watch on his right hand, the watch was also collected. Harper did not see any problem with giving them these items; after all, he wasn't there at the time of the crime.

Newton Gets His Man

Dr. Harper, a distinguished dentist in the community, forgot a basic principle of physics: to every action there is an equal and opposite reaction. Yes, Newton's Third Law of Motion was about to spoil the good doctor's plan. Analysis of the red shirt at the crime lab revealed a radiating pattern of small mist-like blood droplets within the red fabric of the shirt. The victim was shot with a small caliber .22, which would only produce blood spatter for a distance of two or three feet. To get his shot positioned right to hit the aorta, Harper had walked up to within a foot of his wife before he pulled the trigger. Similar analysis of the watchband with Luminol and an ultraviolet alternative light source showed bloodstain on the band. A sample of this blood submitted for DNA analysis established that the blood was that of Alice Harper.

Further Evidence

To solidify the case, they also found gunshot residue (GSR) on the shirt. The potential residue particles were lifted from the fabric with double sided tape, and then subjected to scanning electron microscope analysis. Now the victim's clothing and back were tested for GSR. GSR on Harper's shirt matched GSR removed from Alice Harper. One again, Newton's Third Law came into play in solving this crime.

The doctor's plan to commit the perfect crime was spoiled by a principle he learned in a high school physics class. But more important is that good forensic analysis provided the evidence necessary for another successful conviction.

Web Links:

The Eider Files, The Search for a New Breed of BioTerrorism Weapons, by Doug Hanson

Doug Hanson, Ph.D. is a Ph.D. Biochemist who has operated toxicology and analytical chemistry laboratories for over 25 years. He is also a freelance writer who has written extensively for law enforcement, EMS and first responder magazines. His areas of expertise and written articles include: forensic investigation, DNA analysis, blood spatter, trace analysis, toxicology, drug and analytical chemistry, and forensic anthropology among others. He has written about car bombs, IEDs, soft targets, biological and chemical agents and attack scenarios. He has written on juvenile arson and illegal meth labs. Doug has written and published a book entitled The Eider Files, a novel about bioterrorism.

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