Crime Scene Training

How Crime Labs Restore Obliterated Serial Numbers

 Laboratory Serial Number Restoration

 In many instances criminals will obliterate serial numbers from objects so that ownership may not be traced. Whether it is a handgun or motor vehicle, it takes little effort on the part of the perpetrator to grind off these identifying marks.

 Many objects have serial numbers in the form of labels or placards, which are easily removed but serial numbers that are mechanically stamped into a metal surface, can be restored using the acid etching recovery method.

 When serial numbers are stamped into a metal surface, the metal beneath these stamps is compressed. When the numbers are removed, either by filing or grinding, a relatively smooth surface results. In many cases the perpetrator is satisfied that his task was successful if the numbers are no longer visible. But in reality, the compressed metal still retains these marks.

 The theory behind acid etching is quite simple: When applying an etching reagent, generally a strong acid, the metal around the stamped marks will be etched or eaten away by the acid leaving the compressed metal intact.

Here is the procedure generally followed:

1. The surface from which the stamped numbers were removed must be made smooth so that the etchant will work uniformly. Using sandpaper or emory cloth, the technician was work on this surface until a mirror-like finish results.

2. Etching reagents are available in two forms—liquids and gels. So long as the surface is level with the ground, liquids are the better choice since they work faster. But when liquids are used, it is necessary to build a dam around the area to be restored. Modeling clay is the best medium to use for the dam. On vertical or sloping surfaces the gels are the best choice.

3. There are currently four different reagents—liquid and gel—in use at crime labs: These reagents are specific for etching steel, copper, aluminum and plastic.

 For demonstration purposes, a small piece of aluminum was hand-stamped with a series of numbers. Have pen and paper handy to quickly record the restored numbers as there have been   instances when the restored numbers disappeared after a short time. Using a bench grinder, the numbers were ground off.

 As noted in the sequence listed above, the surface was first hand-polished. Next, the surface was wiped clean with aluminum surfacing solution to remove any aluminum dust present. Due to the testing surface being perfectly flat, no dam was put in place since only a small amount of etching solution was used.

 The liquid etchant is applied using a bulb pipette. Closely observe the object. A slight bubbling action may be noted. After a few minutes, remove the etchant with the bulb pipette and examine the surface for restored numbers. Sometimes running water over the surface helps one to visualize the numbers.

 Record the numbers as quickly as possible.

 One of the instructors in a well-known crime scene technology program tells the story of how serial number restoration saved him a considerable amount of money.

 This instructor was following up on an advertisement for a 1967 Chevy Camero with a 302 Cu. In. engine. He stated that if this vehicle was all original equipment, it would command the asking price of $19,000 (20-years ago). While visiting the seller and inspecting the car, he asked where the engine block number was located. The seller said that when the car was in for maintenance, a mechanic had accidently removed the numbers. HMMMMM!

The instructor, now somewhat skeptical about that bit of information suggested that he and the seller should restore the number and the seller agreed. Using the steel etching gel from his classroom, he made several attempts but the numbers did not reappear. He then decided to take a pass on buying the car. The next day the seller called and told the disinterested buyer that he had left the etching gel on the block for several hours and the full serial number appeared.

 Checking with the manufacturer, the seller learned that the engine block was a replacement and not original equipment, thus saving the instructor about $10,000!

 If you would like to learn more about serial number restoration you are invited to download the technical information manual on a complete serial number restoration kit. Click HERE for a free download.

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

 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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Does Body Language Reveal Deception

Evaluating Truthfulness and Detecting Deception By DAVID MATSUMOTO, Ph.D., HYI SUNG HWANG, Ph.D., LISA SKINNER, J.D., and MARK FRANK, Ph.D. (reprinted from FBI Bulletin, June 2011) While interviewing the suspect who claims ignorance about an incident, the witness who saw it happen, or the informant who identified the perpetrator, the detective asks a question that will eviscerate the perpetrator’s story. As the suspect prepares to answer, he looks up and to the left, purses his lips, tenses his eyelids, and brings his eyebrows down.  The investigator knows that a suspect displaying shifty eyes and gaze aversion and looking up and to the left when answering uncomfortable questions is exhibiting signs of lying. The suspect is not totally disinterested, but he is reluctant to participate in the interview. Because the suspect’s behavior suggests dishonesty, the detective prepares to drill still deeper in the questioning.   Unfortunately, this investigator likely would be wrong. Twenty-three out of 24 peer-reviewed studies published in scientific journals reporting experiments on eye behavior as an indicator of lying have rejected this hypothesis.1 No scientific evidence exists to suggest that eye behavior or gaze aversion can gauge truthfulness reliably. Some people say that gaze aversion is the sure sign of lying, others that fidgety feet or hands are the key indicators. Still others believe that analysis of voice stress or body posture provides benchmarks. Research has tested all of these indicators and found them only weakly associated with deception.2  Relying on false clues, or signs, about lying can have dire consequences.3 It can lead to inaccurate reads that witnesses, suspects, or informants are lying when they are not or that they are telling the truth when there is more to the story. Reliance on false clues leads to misplaced confidence about the strengths and weaknesses of cases and can lead an investigator down dead-end paths. Moreover, a false read can have deadly consequences.   BEHAVIORAL CUES Years of research have led the authors to focus solely on the most verifiable behavioral cues to lying.4Many studies have involved a randomly selected sample of people assigned by chance to lie or tell the truth. Unfortunately, such studies feature participants with no personal, financial, or emotional investment in the lie or any fear of exposure to sanction if they are caught. No stakes are involved—no punishment for getting caught and no reward for fooling the investigator.  The authors’ studies involve people motivated to act against a person or group with a different ideology, placed in a situation where they choose whether to commit a crime (e.g., steal a check made out to the group they despise), and then interviewed by a retired law enforcement officer, offering them the opportunity to tell the truth or lie. The stakes involved include facing detention, enduring blasts of white noise, or, for instance, having the stolen check donated to the group they hate. These consequences would occur if the person were not believed regardless of the truth because, in real life, consequences stem from judgments, not reality.  Thus, truthful individuals often are nervous in police interrogations. The authors strive to make their research practical and analogous to real-world law enforcement situations and have found that, clearly, the behavioral cues to lying differ when people are not vested in having their story believed and have no fear of detection.  The authors monitor their participants with sensors that record and analyze their facial behaviors, gestures, body movements, voice and speech characteristics, physiological indicators (e.g., heart rate, blood pressure, skin conductance, respiration), heat emanation from their faces and heads, pupil dilation, and gaze direction. In addition, the authors record their participants' spoken words and then examine their verbal statements and style. The results have demonstrated that when motivated people lie and face consequences upon detection, clues to deception emerge and appear as leakage across multiple channels. Four of these are nonverbal (facial expressions, gestures and body language, voice, and verbal style). A fifth channel of leakage is in the actual words spoken—verbal statements.  It is not the mere presence or absence of behaviors, such as gaze aversion or fidgeting, that indicates lying. Rather, it is how these nonverbal cues change over time from a person’s baseline and how they combine with the individual’s words. And, when just the behavioral cues from these sources are considered, they accurately differentiate between lying and truth telling.5  The findings from these studies also have clearly indicated that no one indicator of lying exists; if so, research would have identified it by now, and almost everyone could unerringly detect when people lie. Of course, this would put an end to most competitive card games and prove generally destructive to society. No one could be polite, society would not function, and most groups and relationships would fall into chaos.  Because liars facing stakes betray their untruth by leakage that comes across as a complicated mass of signals, investigators make adequately processing this stream of information more difficult when focusing on inconsistencies in the story, rather than how it is told. The problem is that the liar also focuses on presenting a consistent, albeit false, story. Ironically, liars also wrestle with their emotions and thoughts, actively trying to manage facial and body expressions, voice tone, verbal style, and words—all while monitoring the investigator’s reaction. This allows reliable indicators of lies to pop out in the verbal and nonverbal leakage, which investigators often overlook because of their intense focus on the story.  VERBAL AND NONVERBAL LEAKAGE Lies can be betrayed in verbal and nonverbal leakage independently. However, the authors have chosen to further examine this area, analyzing the combined contribution of verbal and nonverbal leakage to the prediction of deception or truthfulness. In their latest study, the authors examined videos of dedicated members of ideologically motivated groups. Separate studies analyzed two types of lies. One involved participants in a situation in which they chose whether to steal $50 in cash from a briefcase and later were interviewed about their guilt (the crime scenario). In another analysis, participants decided to lie or tell the truth about their beliefs concerning their political cause (the opinion scenario). Each instance involved stakes—if researchers judged them as lying, the subjects lost their participation fee and faced 1 hour of white-noise blasts while sitting on a cold, steel chair in a small, cramped room.  The authors selected videos of 10 individuals from each scenario and knew beforehand that half told the truth and half lied. After coding their nonverbal behaviors—facial expressions and gestures—the authors judged their consistency with the speech content according to time and context. The authors also transcribed what the participants said and annotated their statements using the concepts and linguistic features of statement analysis, such as examining minimizing and intensifying adverbs, editing adverbs, alterations in verb tense, equivocation, unique sensory details, and changes in nouns.  Analyses by the authors indicated that the liars produced significantly more nonverbal behaviors inconsistent with the context or content of their words than truth tellers. For example, a participant in the crime scenario may have denied stealing the check, but showed fear or distress while making that claim. Conversely, the nonverbal behaviors (e.g., nodding their heads up and down while saying “yes”) of truth tellers remained much more consistent with their verbal statements. Interestingly, the nonverbal behaviors by themselves were not as indicative of truth telling or lying; instead, it was their level of consistency with the verbal statements or context that determined truthfulness at a high degree.  Also, the various statement analysis categories that were coded could differentiate liars from truth tellers at statistically significant levels. Greater use of minimizing and editing adverbs and changes in nouns and verbs all were associated with lying, while equivocation and spatial details indicated truth telling. These findings confirmed previous research on statement analysis.6  While these findings remained consistent with previous research, the authors also combined the nonverbal leakage and statement analysis cues in attempting to differentiate truth tellers from liars. The authors found that inconsistent facial expressions combined with statement analysis annotations could correctly classify 90 percent of the participants in the videos as to whether they lied or told the truth. This seems to indicate that behavioral cues in both verbal statements and nonverbal behaviors collectively provide a much better source for gauging truthfulness. This potentially provides investigators with powerful aids in conducting investigations and interrogations.7  DETECTION OF LIES Nonverbal Examination Investigators can improve their ability to detect lies by becoming more aware of and skillful in reading the nonverbal cues to lying. In examining such important nonverbal behaviors as gestures, voice, and verbal style, officers first must focus on the facial expressions of emotion, especially those known as micro- and subtle expressions, because these both are involuntary and have demonstrated association with deception.8  Microexpressions are fleeting expressions of concealed emotion, sometimes so fast that they happen in the blink of an eye—as fast as one-fifteenth of a second. This results from the individual’s attempt to hide them. They generally go unnoticed in daily social interactions; the most reliable evaluations are done by the review of slow- and stop-motion videotape of the speaker.   However, people can learn to see them in real time. For instance, trainees at the FBI National Academy typically can increase their recognizion of microexpressions to above 70 percent, in some cases over 90 percent; studies on other populations, including U.S. Coast Guard senior investigating officers, have shown average posttraining accuracy of better than 80 percent.9 These same officers almost doubled their ability to accurately read individuals who displayed these microexpressions in real-world, real-time settings. This ability is retained weeks after initial training.10Facial expressions of emotion, including macro-, micro-, and subtle expressions, are universal and independent of race, culture, ethnicity, nationality, gender, age, religion, or any other demographic variable. All people express emotions on their faces in exactly the same ways. Moreover, they are immediate, automatic, and unconscious reactions. These are incredible characteristics of facial expressions because learning to read them means that someone can have a bigger window into the soul of almost anyone. It is a powerful tool for investigators because facial expressions of emotion are the closest thing humans have to a universal language.  Statement Analysis Investigators also can improve their ability to detect lies by becoming skillful at statement analysis, which applies internalized grammatical rules that stem from the language acquisition part of the brain to an individual’s written or spoken words. In fact, people apply these rules to what they read and hear every day when they make a judgment about whether or not something is truthful or deceptive. While people may say that their belief is based upon their “gut,” in reality, their brain is applying these internalized grammatical rules to the information. By doing so, investigators can gain valuable insight into a person’s thoughts, motivations, and ideas. Statement analysis involves examining several aspects of someone’s words, including verbs describing communication and uncompleted action; changes in verb tense; minimizing, intensifying, and editing adverbs; extraneous information; unique sensory details; and statement structure, which identifies the person’s focus—on the incident or somewhere else. Research has shown that distinct differences exist between a deceptive statement and a truthful one. By using the techniques of statement analysis, investigators can more readily detect truthfulness or deception in an individual’s words. With these insights, investigators become more efficient and effective in their abilities and gain better focus on the investigation.  Proper Perspective Investigators must remember that no “silver bullet” for identifying deception exists. Detecting microexpressions or inconsistent facial expressions of emotion and identifying areas of interest in a verbal statement via statement analysis never should be considered indicative of lying by themselves. Instead, they comprise tools that officers can use to guide them through an interview or interrogation. They help identify areas that need further probing—concealed thoughts, feelings, opinions, and omissions of parts of the story. But, investigators should keep in mind that these behaviors could result from reasons other than lying; perhaps, the suspect or witness feels embarrassed or fears retaliation by talking to the police. Or, maybe, the officer has not established a relationship or has physically threatened the suspect. This shows the importance of building rapport; it reduces the amount of ambient anxiety found in any law enforcement interview. Thus, recognition of facial expressions of emotion and statement analysis represent important tools that investigators can add to their toolkit to help them conduct interviews and interrogations more efficiently and accurately. But, like any such tool, they need to be supplemented with corroborating statements, physical and forensic evidence, and hard work. And, in the authors' experience, the best lie catchers do not jump to conclusions early based solely on facial expressions or word usage. Instead, they use them as a guide through an interview to get the best information possible. This enables further elicitation of information and better comparisons and contrasts with other statements and physical evidence—all of which lead to more informed decisions.  PRACTICAL APPLICATIONS Training and practice can help individuals and groups leverage facial expressions of emotion, other nonverbal behaviors, and statement analysis to better evaluate truthfulness, detect deception, and assess credibility. Improving these skills makes for a better interviewer and investigator. Although difficult, mastering such methods can make the officer faster, more efficient, and more accurate in conducting interviews. Investigators can follow some pointers to apply these skills in their police work.  If, while interviewing suspects, witnesses, or informants, investigators see a microexpression inconsistent with the words spoken or the emotions described, they should follow up until they can achieve reconciliation or get a more complete answer. For example, if suspects flash fear, distress, or contempt when saying they were nowhere near the scene of the crime, they may be omitting some of the story. Interviewers should probe that particular statement.  Similarly, if suspects show disgust when talking about another person, what does that mean? It depends on the context. Saying, for instance, they are “not a fan” of someone suggests that they truly dislike the individual. A statement like “He’s a great guy” suggests the suspect is lying.  Informants who show contempt when investigators request of them a particular action show a level of distrust. This suggests a need for better rapport before officers make the request.   When witnesses leak expressions inconsistent with their statements, their emotions show investigators how to dig deeper to unearth the hidden story. For instance, flashing fear when talking about the suspect may indicate that a witness feels threatened by the individual and, thus, apprehensive about sharing all details. Or, witnesses may fear getting caught lying about their relationship to the suspect. Regardless, something about the suspect has produced an involuntary reaction in the witness. If investigators identify the emotion, they can leverage it to obtain the real story.  After taking a written statement from a suspect, investigators should apply statement analysis techniques to identify key areas to pursue in the interview. For example, if a suspect’s statement jumps in sequence from the early evening to the next morning, ignoring the time that the crime occurred, it likely would be noted by editing adverbs (e.g., then, later). Additionally, noting changes in noun and pronoun usage and verbs of communication can prove critically important as they can signify areas for further exploration. Once officers complete their analysis, they can begin the interview by jumping straight to such areas in the statement, thereby catching suspects off guard because of the immediate attention on the part of their statement where they feel vulnerable.   When questioning the suspect, investigators should watch their emotions and other nonverbal behaviors. Signs will arise that something meaningful was glossed over. For instance, suspects showing fear or distress when officers jump straight to a particular point in time may indicate that there was something to hide. Conversely, displaying surprise or, perhaps, nothing, may show that the skipping was incidental.  When an interview turns into an interrogation, officers can use the signs of emotion to know when to push further or retreat. For example, if suspects show anger, contempt, or disgust, it may, but not always, be best to stop and try another approach. However, if they show fear, it might be time to drill deeper. If they show distress, they may be about to call it off. In this instance, investigators should use logical reasons as to why the suspect may have committed the crime and continue to press for the confession. Understanding facial expressions also can let investigators know when someone fakes an emotion. Sometimes, a person may express anger at being accused. Is it real? A liar more likely will fake anger. Officers who know all of the signs of anger more accurately can determine the authenticity of anger. The same rules apply to happiness. There is a reliable signal within a smile for a genuine feeling of happiness, and, if investigators know that, they can tell whether a person who says they feel very happy at that moment actually are experiencing happiness.  CONCLUSION Because of the subtlety of microexpressions, other facial expressions of emotion, and cues in verbal statements, investigators must devote focused attention to detect them. In many situations, interviewers focus primarily on a suspect's story, rather than how they tell it or what they show while conveying it. Investigators must do more than simply be aware of expressions while not allowing such multitasking to dilute their skills. With training and practice, investigators can become more aware of what they see in the form of microexpressions and hear as they apply the concepts of statement analysis. Officers should become aware of microexpressions and how to spot them, as well as the basic techniques of statement analysis. They should learn them well enough so that they become automatic and, rather than interfere with their processing of interviews, augment their skill set. In doing so, they will be armed with powerful investigative tools that leverage the most cutting-edge  science available.  Endnotes 1 C.F. Bond, A. Omar, A. Mahmoud, and R.N. Bonser, "Lie Detection Across Cultures," Journal of Nonverbal Behavior 14 (1990): 189-204. 2 B.M. DePaulo, J.J. Lindsay, B.E. Malone, L. Muhlenbruck, K. Charlton, and H. Cooper, "Cues to Deception," Psychological Bulletin 129, no. 1  (2003): 74-118. 3 The use of popularly held beliefs about indicators of truth and untruth still proves relevant for investigators, particularly if others, such as suspects, believe them and investigators can leverage those beliefs to obtain truth. 4 M.G. Frank, T.H Feeley, T.N. Servoss, and N. Paolantonio, "Detecting Deception by Jury, I: Judgmental Accuracy," Journal of Group Decision and Negotiation 13 (2004): 45-59. 5 M.G. Frank, "Thoughts, Feelings, and Deception," in Deception: Methods, Motives, Context, and Consequences, ed. B. Harrington (Palo Alto, CA: Stanford University Press, 2009), 55-73; and M.G. Frank, M. O'Sullivan, and M.A. Menasco, "Human Behavior and Deception Detection," in Handbook of Science and Technology for Homeland Security, ed. J.G. Voeller (New York, NY: Wiley and Sons, in press). 6 A. Vrij, "Criteria-Based Content Analysis: A Qualitative Review of the First 37 Studies," Psychology,Public Policy, and Law 11 (2007): 3-41. 7 Moreover, post hoc forensic analyses of the 10 percent misclassified strongly suggest a unique role for minimizing and editing adverbs. These occurred in individuals relatively sparse in their expressivity, as well as verbal output. Thus, the cues to deception in such individuals may be very subtle, and the authors believe that one area in which such cues may occur may be in the use of minimizing or editing adverbs. 8 M.G. Frank and P. Ekman, "The Ability to Detect Deceit Generalizes Across Different Types of High-Stake Lies," Journal of Personality and Social Psychology 72 (1997): 1429-1439; and G. Warren, E. Schertler, and P. Bull, "Detecting Deception from Emotional and Unemotional Cues," Journal of Nonverbal Behavior 33 (2009): 59-69. 9 M.G. Frank, D. Matsumoto, P. Ekman, S. Kang, and A. Kurylo, "Improving the Ability to Recognize Microexpressions of Emotion" (manuscript submitted for publication). 10 D. Matsumoto and H.S. Hwang, "Training the Ability to Read Microexpressions of Emotion Improves Emotional Competence on the Job" (manuscript submitted for publication). Read original article on FBI website Sign up Here for E-Mail Alerts

How Forensic Evidence is Presented to a Jury

Forensic Evidence is The Eyewitness

Author: Jack Claridge - Updated: 20 July 2010 www.ExploreForensics.co.uk/

There are many different ways in which evidence can be presented to a jury in order for them to fully understand the nature of what they are being told or shown.

These methods may include the use of visual aids, video footage, still photographs, catalogued pieces of evidence (referred to as exhibits), audio recordings, transcripts of conversations that have taken place and also maps and handwriting.

Any of these methods may be employed during the course of a trial and depending on the nature of the trial - and indeed the severity of the crime - it may also be necessary for the jury to visit the scene of the crime.
Visiting the Crime Scene

If the crime being tried in court is that of murder - and in particular a series of particular brutal murders - then it may be necessary for the jury to visit the scene - or scenes - of crime to gain more of an understanding into the nature of the killings.

This normally happens in trials of so-called serial killers; a serial killer is defined as an individual- 
or individuals - who have committed a series of murders using the same Modus Operandi (MO) over a defined timescale. Serial killers are normally creatures of habit and can return to the scenes of their crimes more than once, thus showing the jury these crime scenes can - in conjunction with expert testimony - can assist the jury in gaining valuable insights into their character and their motives.
Video Evidence

Video evidence is now employed in many courtrooms across the United Kingdom (and the U.S.A) as a means of protecting not only the identity of those giving evidence but also as a means of saving money. Witnesses may not be able to attend a trial for a variety of different reasons but may be able to attend their local court where a video link will provide them with two-way audio and visuals of the trial proper.

Also evidence recorded onto video such as those films recorded on digital camera or video camera may be submitted to the court as evidence. In instances such as terrorists attacks such evidence is invaluable in order to build up a picture of what happened before, during and after such an attack took place.

Again it is worth noting that all evidence submitted for a trial must be relevant and should not be based on supposition or hearsay; circumstantial evidence as it is known is not reliable and therefore both defence and prosecution counsels are likely to ask for its exclusion from any criminal proceedings.

Most of us will have heard the term Ballistics at some time or other - more often than not when we have been watching fictionalised accounts of police work on television or in the cinema.
What is Ballistics?

Ballistics is the area of Forensic Science that deals with firearms; how they are used, why they are used and why they are used frequently in the practice of murder.

What many people do not realise is that when a person is shot the wound and the condition of the victim can tell a lot about the nature of the weapon that has been used. Indeed if the weapon has been left at the scene of the crime - which sometimes happens when the perpetrator panics - the weapon itself can go a long way to providing valuable information as to the kind of person who has committed the offence.
Identifying a Weapon

Most guns have their own unique identifying features and even if the gun has not been left at the crime scene many degrees of information can be determined from the bullet, the nature of the wound and any residue that is left around it.

Bullets contain a mixture of gunpowder and cordite and these leave burn marks on the skin of the individual either wounded or killed, they also leave a fine residue on the fingers and hands of the individual firing the gun. These burn marks can signify closeness of the victim to the perpetrator, kind of weapon and also if the weapon has had any modifications made to it. Some weapons have been disarmed by having the firing pins and mechanisms removed but there are individuals who can 'reactivate' these weapons for use again.

Also, each weapon's barrel contains small ligatures and grooves, which, when a bullet is fired from them, make marks on the shell casing, which can be used as a means of identifying the make and model of gun if these shell casings are found at the scene.

It is also worth noting that an automatic - or semi automatic weapon - will expel shell casings as the weapon fires a round whereas a revolver will fire the round but retain the shell casing within the barrel (cylinder).
Investigating

The field of ballistics is able to identify rifling patterns, marks made by using suppressors (silencers), shell casings, powder burn and many other different areas relating to the use of firearms and the evidence they leave behind.

Indeed most ballistics experts will be able to tell you the particular weapon simply by the sound of it being fired. They will also be able to carry out distance and depth tests which include firing rounds of ammunition into water, sand and other substances to determine how close a person would have to be to receive a life threatening wound from a gun.

Ballistics is a very important part of the world of Forensic Science and much of its evidence is used in criminal proceedings. In some cases the use of ballistics research can prove a link between many different crimes carried out over a lengthy period of time. This is also an important function of the ballistics team as many weapons are passed and sold on between criminals during their life cycle.

 

 

 

 

 

 

The Fingerprint Sourcebook

Answers to Questions About Fingerprints

by Scientific Working Group on Friction Ridge Analysis, Study and Technology (SWGFAST), et al. March 2011

The principle goal of the Fingerprint Sourcebook is to serve as a compendium of up-to-date information resources covering the science of fingerprint identification. The Sourcebook is the brainchild of the International Association for Identification (IAI) and this work covers  the anatomy and physiology of friction ridge skin, proper method for recording exemplars from the living and the dead, latent print development methods, factors in expert identification, legal issues and much more,

The text will eventually consist of 15 chapters, and at this writing, 13 chapters are a reality and have been published.  The Fingerprint Source is being made available via the website of the National Institute of justice (NIJ) and is published  pdf  for immediate download by chapter.

To download the completed chapters.   Visit the NIJ Website Here

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Hair and Fiber Evidence

Hair and Fiber Evidence

Author: Jack Claridge - Updated: 2 October 2010 http://www.ExploreForensics.co.uk/

We have all doubtlessly watched television shows and/or movies where the mention of hair and fibre is made often when it comes to the discovery of a corpse or indeed the reporting of a crime.

The Importance of Hair and Fibre
Hair and fibre are two of the most important resources in Forensic Science and are often responsible for providing valuable clues as to the identity of an assailant or attacker.

The discovery of hair on the body of a victim or on the clothes of someone who has been the victim of an assault can often be used to determine race and sex. It can also be used to extrapolate DNA for comparison.

Although hair is classified as benign dead matter it still contains DNA even though the hair itself is not actually a living organism but is merely pushed through the follicles of the scalp, arms, legs or any other part of the anatomy where hair is found.

Fibres too are an important discovery and can go some way to determining what an attacker or killer was wearing at the time of the incident. Many forensic scientists use fibres as a means of determining the nature of the item worn and in some instances can be as precise as to identify the make of the garment and thus the manufacturer. In some instances this technique is so successful that garments that are rare or indeed specially made can be identified and thus a list of possible suspects drawn up simply by the number of units sold.

Collecting Evidence
Hair and fibre are collected at varying points throughout the forensic science process but most notably at the scene of the crime and at the autopsy stage.

At the scene of crime hair and fibre samples are collected from the surrounding area and this can be for the purposes of eliminating individuals from police enquiries as well as to help narrow down the list of suspects. These samples are collected through meticulous and painstaking processes, which are carried out by Scenes of Crime Officers (SOCO) who themselves are dressed in protective clothing so that their own clothing and hair do not contaminate any evidence with may pre-exist.

These samples are collected in varying vials, tubes and grip seal bags so that cross contamination may not occur between the time of collection and the time of proper analysis.
The victim's clothing may be examined for trace elements of bodily fluid such as blood, semen or saliva and whilst this is being done the clothes are also checked for hairs that do not match those of the victim and likewise fibres that are not correspondent to the items of clothing they are wearing. It is also possible at this point to collect animal hair and soil samples.

The second stage of collecting hair and fibres is at the autopsy when the pathologist will scrape the underside of the victim's fingernails for any hair, skin, fibres or material that might have gathered there. This is a useful technique as often during a violent struggle the victim with attempt to defend him or herself by lashing out in a defensive posture, possibly scratching or biting their attacker in the process.

These materials are then collected and stored in the same manner so that further examination and comparison may take place at a later stage.

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