Crime Scene Training

Crime Scene Evidence-Convictions are Rare Without Physical Evidence From the Scene

How Crime Scene Evidence Can Make Your Case

By: Don Penven, Tech Support Group

Sensational homicides are populating the National news of late, and crime scene evidence seems to play a key part in many courtroom decisions. Numerous TV “Cop Shows” draw bigger and bigger audiences as the viewing public develops an insatiable appetite for the "blood and guts” of crime scene investigation. 

Crime scene investigation (CSI) includes some basic methods that include forensic applications, photography, chemistry, physics, mathematics and just plain common sense. “How to Become a CSI” is a fast-growing industry among institutes of higher learning offering on-line diplomas and degrees in the discipline. 

One fact is certain: No two crime scenes are very much alike.

 Crime scene investigation must follow an orderly protocol—otherwise physical evidence may be misunderstood, mishandled, or missed altogether. The basics steps taught to crime scene investigators

by many educational sources include, but are not limited to the following steps:

1. Protect Life and Property. The first responding officer(s) must take the steps necessary to protect life and property. First aid is rendered to the injured and aid in the form of emergency medical teams, crash-rescue units, fire departments and backup officers are summoned.
2. Secure the Scene. Officers must take steps to prevent damage to, or disruption (contamination) of the scene. Many experts in this field state that more harm is inflicted on crime scenes by the presence of law enforcement officers than from any other source. The first officers on the scene must make a quick determination of what constitutes the boundaries of the scene, and will then take steps to protect this area. This is where the inevitable “Yellow Crime Scene Tape” is introduced into the crime scene. Sentries must be placed at all possible points of entry and access will be denied to all not having a legitimate reason for entering the area.
3. Brief the Investigators. Except in very small law enforcement agencies—where the first responders may also wear the hats of crime scene investigators, the first responders will brief those on hand who will assume control of the scene and perform evidence search and collection. This briefing includes any observations made by initial officers and will relay statements made by by-standers, witnesses and victims.
4. 4.       Conduct a Walk-Thru of the Crime Scene. The walk-thru is a time spent making visual observations throughout the scene. Physical evidence can be in plain sight (weapons, spent-shell casings, blood, impression evidence (hand and footprints), etc. The investigator will make notes as potential crime scene evidence is revealed. The walk-thru skirts the perimeter of the areas where obvious physical evidence resides. All the while, the investigator is conscious of the fact that a great deal of evidence may be present that is not in plain view or is invisible in nature. Thus he must avoid walking through areas that may harbor footprints in dust, weak or invisible bloodstains or blood spatter and latent fingerprints. 
5. 5.       Recording the Crime Scene. Recording the scene most often begins with CSIs preparing a rough sketch of the area. Locations of furniture and other building contents are included as well as apparent items potentially useful as crime scene evidence. Outdoor scenes present different challenges so nearby vegetation, trees and similar fixed and moveable objects are sketched. Next comes photography. Overall, wide-angle photos record the scene prior to any efforts to locate physical evidence. Medium distance photos follow that show relative positions of evidential items with regard to each other, and then close-ups record specific items. Many agencies also use video to supplement still photographs. As far as human nature is involved, a jury’s rapt attention is often stronger when videos are used to depict the scene. Video provides a sense of actually being at the scene for jurors. 
6. Processing the Scene for Physical Evidence. This is the nitty-gritty phase of the investigation. Often, specialists skilled in locating and recovering dust impressions are joined by latent fingerprint technicians who will ply their expertise. In violent crime scenes, a blood spatter analyst will go to work.
7. Collecting the Physical Evidence. It is one thing to locate potential evidence, and it is another to gain the usefulness this evidence may possess. Collecting techniques may include an electrostatic dust print lifting system, superglue fuming of various items in order to reveal invisible latent fingerprints, and there is also a mix of physics and geometry when analyzing and recording blood spatter.
8. Packaging and Transporting Crime Scene Evidence. Much of the evidence collected at a crime scene is very fragile in nature. This evidence may be damaged by handling and the packaging method, and it may deteriorate or “spoil” due to improper storage. Physiological fluids, and their potential for providing DNA profiles, are especially fragile and easily susceptible to damage or deterioration. 

While some TV shows run through all of the above steps in just 45 minutes or so, it is apparent that investigating a crime scene can take many hours or even several days from start to finish.

 

The National Institute of Justice has performed in-depth research into the “CSI Effect.” This is based on the premise that juries are being conditioned to expect to see the very same techniques used by TV actors to be employed by the real-life cadre of CSIs. What the general public expects to see are scientific principles and equipment resulting in “Slam-Dunk” prosecutions, while failing to comprehend that many of the techniques depicted on TV require extensive, virtually unlimited budgets to accomplish. See The NIJ video.

 Most law enforcement CSIs are adapting to the budget crunch, and they are still able to bring the guilty to justice through their dedication and perseverance—despite the lack of sufficient funding.

 Many law enforcement agencies have been forced to limit training and are coming to recognize that a great deal of specific crime scene training is available to them at no cost. The CSI Tech Blog offers specific training in Crime Scene Evidence disciplines, and it is a trusted source for learning the many techniques and procedures needed by today’s crime scene teams. 

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Bullet Trajectories at Crime Scenes

 By: Don Penven, Tech Services Group 

Recommended Procedures for Documenting Bullet Trajectory

Crime scenes involving the use of firearms present unique challenges for the crime scene investigator, but using relatively simple techniques it is often possible to reconstruct the events that give some indication as to what occurred during the actual discharge of the weapon. By this I mean it is possible to determine the actual path or trajectory of the bullets, and using this information, determine the location of the shooter. 

A number of factors must be taken into account including the position of cartridge cases ejected from automatic and semi-automatic weapons. It is therefore essential that the exact position of spent casings be marked and documented before any other investigative procedures are followed. 

Document (Photograph & Sketch) Positions of Spent Cartridge Casings 

Photography is the first necessity so it is imperative that the crime scene be afforded absolute security. Until spent cartridges are properly recorded—all foot traffic must be banned from the area. 

Each spent casing should be marked using standard crime scene evidence identifiers such as “evidence tents,” placards, or similar devices. 

Typically, overall scene photos are taken first, followed by medium distance and close-ups. Be certain to include other nearby objects in these photos to better establish the true position of each object photographed. 

It is also imperative that a crime scene sketch be prepared once photography is completed. Each spent casing should be located on the sketch that includes either triangulation or coordinate methods of measurement (See: “Sketches and Detailed Drawings of the Crime Scene,” TB-100 (Download Here) http://www.sirchie.com/Assets/Manuals/pdf/TB100_TB03-175ENG.pdf 

The physical location of spent casings may tell a unique story of their own. Placement of these objects results from normal ejection by the weapon and may provide limited data as to the location of the shooter, the direction of shots fired and possibly the path taken by the bullet(s). Ejected casings may also substantiate or refute statements from witnesses, victims or suspects. 

Methods For Determining Bullet Trajectory

Historically, the technique of “stringing” a crime scene may date back over 70 years. Stringing has been, and continues to be used at crime scenes for the purpose of determining the source of blood spatter and the path of bullets. 

Normally speaking, a firearms examiner would be called upon to render expert testimony with regard to the physics and trigonometric calculations regarding bullet travel. But experts with these qualifications are often few in number. It is therefore incumbent upon the crime scene investigator to provide this “expert” with the documentation needed to draw his conclusions. 

While other factors may contribute to a determination of bullet trajectory—the most important fact required for there to be even the slightest degree of accuracy is for the bullet(s) to have passed through at least two objects. This will include:

• A door and a wall
• A two-sided wall
• A window and/or a wall, door or victim, etc. 

While stringing the crime scene has been the most frequently used method for documenting bullet travel, it does have its short-comings. When a bullet passed through a window, sharp edges are created, therefore if string is used it must be protected (tape or drinking straw). If more than just a few feet of travel is involved, string is susceptible to droop or sagging. It is therefore advisable to use a strong nylon or other synthetic string rather than cotton string. 

Alternatives to Using String

An ideal alternative to use are rods of different diameters. With the exception of hollow aluminum rods, most metals like steel, copper or brass may tend to be too heavy. Also consider wooden dowels or plastic and fiberglass rods. 

Tools and Equipment Needed for Determining Bullet Trajectory

• String (if this is all that is available) Nylon (or equivalent synthetic)
• Plastic or fiberglass rods (preferred), multi-colored if possible)
• Adhesive tape (duct tape, surgical tape, even fingerprint lifting tape)
• Measuring tapes (25-100 ft. w/metric scale)
• Photo ID tape or stick-on labels
• Evidence collection kit containing sterile swabs and collection containers
• Evidence marking labels (adhesive-type)
• Protractor (clear plastic) or,
• Inclinometer – for measuring angles and slopes
• Directional compass (camping-type with aiming sight)
• Graph paper for sketching
• Marking pens
• Carpenter’s or brick mason’s string (bubble) level. This device is only used if an inclinometer is not available.
• Laser pointer 

Crime Scene Investigation Guidelines

Due to the variety and complexity of crime scenes, it is impractical to publish specific guidelines. The following guidelines are offered as a starting or reference point. The actual methods and procedures followed will be dependent upon the experience, judgment and training of the crime scene investigator. 

Interior Structures and/or Motor Vehicles

The procedures followed when investigating shootings that occurred in a structure or motor vehicle are quite similar. Again, these suggestions are meant to be a starting point and the investigator should—first and foremost—follow departmental guidelines and procedures. 

• Shot or shots fired through a glass window: By examining the bullet hole, determine if the bullet was fired from outside or inside the window.
• Using a sterile swab, collect any possible gunpowder residue from around the bullet hole from the outside. Repeat this procedure, using a fresh swab, on the inside of the window.
• Locate any bullet holes inside the structure or vehicle.
• Photograph all bullet holes found in the structure and vehicle. Be certain to include a scale and visible marker (stick on label) adjacent to each bullet hole:

1. Overall, wide angle photos

2. Medium distance photos

3. Close-up photos showing scale to determine bullet hole size

• Determine if the bullet is lodged in the wall or object it struck. Locate the exit hole, if any.
• If string is used, run the string from the bullet hole in the glass to the interior hole. Anchor the string outside of the window by tying it to a pencil, pen, etc., for support. Protect the string with tape or a drinking straw where it passes through the glass. Fasten the other end of the string to the wall or object adjacent to the bullet hole using tape. Photograph the string from a distance, attempting to get the entire run of the string.
• If rods are used (preferred method) insert the rod into the entrance hole and through to the exit hole. Photograph the rod in place. Use the inclinometer to determine the angle of the rod to the wall and photograph it.
• Prepare sketches as needed with all measurements required to give a full understanding of the reconstruction. 

Note: If cartridge cases are found inside the structure, this will indicate that shooting also occurred inside. A thorough search of the room(s) involved is needed to locate additional bullet holes. Repeat the steps above as they apply to the indoor situation. 

At no time during this preliminary evidence collection procedure should any attempt be made to recover the spent bullets that may be lodged in walls, ceilings, doors or furniture. Not until all of the above procedures are completed and photos and sketches finished should spent bullets be recovered. 

Obviously extreme care must be taken to recover spent bullets. The area where the bullet is lodged (wall, door, furniture, etc.) must be cut out using hand tools. Despite the methods often shown on TV, this is not the time to dig out the bullet using a pocket knife. What is needed is a hand drill to make lead holes and then a keyhole saw to cut around the bullet hole. A sharp knife will be needed to cut into cloth furniture. 

Laser Usage

A small laser or laser pointer is also very useful at certain crime scenes for determining bullet trajectory. The laser has, in many instances, replaced the use of string. Some crime scene kits contain a laser that has been modified so that it can be directly attached to the rod protruding from
a bullet hole or attaching it to an inclinometer. One drawback of the laser is that the light beam is often invisible in well-lighted interiors. 

This factor can be overcome by using “canned laser (aerosol) smoke.” The alternative is to darken the room and taking time exposure photos.

Conclusion

Stringing the crime scene during reconstructing is a relatively simple, inexpensive, and accurate method of demonstrating bullet trajectory. It must be emphasized, however, that this determination is not precise, but it is more of a general, or relative, position-fixing method. The use of string is still valid and remains as only one of several methods of determining the point of origin of a gunshot. When feasible for use in court, it remains an excellent demonstrative tool.

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Download the technical information bulletin on the Laser Trajectory Kit: Download LTF100

References

Tomboc, R. C. Using the Trajectory Kit with Trajectory Laser Pointer. Presented at the 79th Annual Conference of the International Association for Identification, Phoenix, AZ, July, 1994.

 Crime Scene Investigator Network, Stringing a Crime Scene to Determine Trajectories, <http://www.crime-scene-investigator.net/trajectories.html> February 9, 2011

Alexander Jason, Shooting Incident Analysis & Reconstruction, <http://www.alexanderjason.com/>   February 9, 2011

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What is Forensic Entomology—and How Can it Solve Crimes

Can Insects Talk? At Crimes Scenes They Can Speak Volumes 

Forensic entomology had its beginnings way back in the 1300s, but during the last few decades it has been given a more serious look by criminal investigators. It is the study of insects that provides a relationship to the acts of criminals. Forensic entomology is basically involved with death investigations, but in recent cases it has been used for the detection of drugs and toxic substances and in some case to pinpoint the actual location where the crime was committed.

 Pathologists and crime scene investigators alike attempt to determine the approximate time of death, as this knowledge can either substantiate or disprove a subject’s alibi.

 The insects found on or around a cadaver can provide an estimate as to how long ago death occurred. The outcome of such an investigation will provide a range of time. This estimate may be a few hours to days or months to bodies that died several years ago.

 The science involved here is to use insects to give a minimum Post Mortem Interval (PMI), which is based on the rate that certain insects mature. Once they hatch from eggs, some insects have an immature stage—better known as the “maggot stage.” Movement during the maggot stage is very limited, but as adults these animals become more mobile than most animals on this planet. These same insects have developed the ability to hatch from eggs, pass through the maggot stage and become mature adults while reaching maturity on dead creatures including humans.

 The most common insects that are often first to appear at a death scene are the various species of blow flies.

 According to NC State University, depending on the ambient temperature … maggots usually complete development in 4 to 10 days, and then their larvae burrow in the soil and pupate for up to a week. Adult flies emerge from puparia and make their way to the surface of the soil. About a week later, females begin to deposit eggs and the life cycle is repeated.

 The entomologist seeks to recover these insects at every stage of their development, as they are a valuable tool used in a toxicological investigation. A mass of maggots can quickly skeletonize a cadaver in a brief period of time. As a body begins to decay, body fluids like blood and urine and soft tissue quickly disappear. When only a greatly desiccated corpse is discovered, the only toxicological evidence remaining will be inside the insects themselves.

 So time is of the essence and the entomologist must busy himself collecting as many samples as possible at various stages of their development. Because many insects will assimilate drugs and poisons that build up in human tissue prior to death, a toxicological evaluation can recover them.

 Another valuable clue is that DNA evidence can be extracted from the digestive tracts of insects. And if physical violence occurred between the deceased and the perpetrator, DNA from that subject may also be recovered—proving a link between the suspect and the body.

 An entomological investigation of a death scene is conducted using the following steps:

Outdoor Locations:

1. Observe the general area and location of the body. Describe the location based on surrounding vegetation, proximity to roads or paths. Make a meteorological investigation to determine temperatures on various parts of the corpse, and general weather conditions over a period of time.

2. Observe the infestations of insects on the body and what stages of development are observed: eggs, larvae, pupae and/or adults. It is also important to become aware of other insects such as ants and beetles.

3. Collect samples of live and dead insects for analysis as well as digging into the soil around the body to locate and collect pupae.

Indoor Locations:

A. Make notes of whether doors and windows are open or closed. Ascertain the room temperature. Determine if the initial responders to the scene may have been responsible for opening or closing them

B. Repeat Steps 2 and 3 above.

Before responding to a dead body investigation, the entomologist should check his equipment and supplies, being certain to have sufficient numbers of evidence containers to be used to collect insect samples.

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Cyanoacrylate Fuming—A Mainstay of Crime Scene Investigation

Developing Latent Prints With Superglue

In the late 1970s, members of the US Army CID Lab in Japan brought home a novel method for developing latent prints. The forensic scientists in the Tokyo National Crime Lab had discovered that the fumes from cyanoacrylate adhesives (CA) or superglue, reacted with the moisture of latent fingerprints in such a way that a latent print on a non-porous surface was covered with a hard coating that encased the delicate ridge structure of the latent print.

 Today, at least here in the U.S., superglue fuming is a basic step in the crime-solving playbook for a majority of crime labs. Back in the early days of superglue research, fuming chambers ranged from large plastic bags to converted fish tanks. Many new, more functional appliances are now available.

 The pros and cons of employing superglue fuming are many: On the PRO side—it protects fragile latent prints by resisting accidental bumps and scuffs that would damage the ridges, it encapsulates the moisture content of a latent thus preventing vaporization and it is a means of processing large quantities of evidence at one time in all shapes and sizes. 

 On the CON side; superglue fuming produces white latent prints that often require the addition of a contrasting color to enable better viewing and photography of the latents, and it leaves a white residue on many of the surfaces the fumes contact. Although some early literature indicated that the fumes may be toxic, this theory has been disproven. The fumes are noxious but not dangerous.

 Over the years many innovative advances have grown out of basic research employing superglue. Among some of the best ideas is vacuum fuming. Researchers discovered that superglue is a top performer when evidence and a few drops of superglue are sealed into a vacuum chamber. Current users of the vacuum fuming method report that is possible to fill a chamber with numerous articles, including evidence such as large plastic trash bags, and cramming in all that will fit seems to have little or no effect on getting excellent results. 

During the first few years of superglue experimentation, researchers sought a means of accelerating the development. Faster is better—right? Not necessarily. One of the first acceleration methods was impregnating cotton pads with a sodium hydroxide solution. This did indeed produces near instant clouds of white smoke. But over time such use fell into disfavor due to health-related concerns. 

Two of today’s most popular methods for superglue acceleration are:

1. Apply superglue to untreated cotton pads. This is quite safe and provides much faster fuming than just placing a few drops of glue       inside a fuming chamber.                                                                

2. The application of heat is quite effective in speeding up the development process. This is accomplished by using a small coffee warmer. More sophisticated fuming chambers have built-in heaters.

 A number of crime labs are encouraging crime scene investigators to fume fragile evidence prior to packaging for transmittal to the crime lab. This step has probably saved countless numbers of latent prints from being accidently destroyed during shipment to the crime lab.

Cyanoacrylate fuming is the number one choice as a first step in locating latent prints on non-porous surfaces. Until something better comes along, the crime scene technician should consider adding this process to the crime scene equipment kit—if this hasn’t been done already.

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