Evidence Law And Psychology: Research Paper

Type of paper: Research Paper

Topic: Crime, Criminal Justice, Law, Psychology, Social Issues, Evidence, Court, Polygraph

Pages: 10

Words: 2750

Published: 2021/02/19

Discussing the Evidential Value and Court Admittance of Polygraphs and Profiling

Human beings have been trying to understand the behaviors of other human beings since the beginnings of communal living. No doubt these issues surrounded problems like, “he said/she said,” which means that two people are telling two very different stories of a single event; however, the two stories are antithetically different. One person may be lying and one telling the truth, but which is which and how best can equity and justice be served. Why are some people unwaveringly honest, loyal and helpful, while others are dishonest, deceptive and counterproductive to society? People commit innumerable illegal acts on a daily basis all over the world. The establishment of laws, court systems and the enforcement of these rules and consequences became a staple necessity of every civilization from ancient time to present day. Of all the types crimes that one may commit there are some that are deemed the most heinous. Those crimes that involve violence and result in permanent damage or death are deemed the most heinous. Sexual assault, child molestation, torture, and cold blooded murder are serious crimes that are the most disturbing and garner, of course, the most extreme penalties. However, while the legal system sentences wrong-doers, society as whole, struggle with the motivations and influences that cause some people to live unassuming, legal and harm-free lives, while others can conceive and commit the most deviant crimes against innocent men, women and children. For decades the field of psychology has been dedicated to the task of researching and de-mystifying human behavior, both psychologically and physiologically, to determine and, even, predetermine the nature of deviant, violent and dangerous behaviors of certain individuals. Over the years, science and medicine have worked to explain these behaviors and gain both, proof and evidence, of their crimes and the motivations behind them. This has spawned two specific contributory aspects, the development of the polygraph examination, or lie detector test, and the psychological profiling of criminals by using the psychological behaviors and cues (Grubin , 2010). However, while, both, of these implementations have been and continue to be accurate and beneficial evidentially, they are not wholly supported as viable and reliable evidence in criminal cases and are not admissible in many court rooms. While their value continues to be debated, there is still much about human behaviors we do not understand, but the contributions of both polygraph exams and the application of profiling have benefitted and bolstered the focus on perpetrators that they may not have otherwise had.


Over the last several decades television has had an invested interest in the fields of law enforcement, court proceedings, investigations and outcomes of crimes, Both in the real-world documentaries and scripted dramas, the procedural crimes programs are everywhere and include popular shows, like “Law & Order,” “NCIS” and “CSI.” However, such programming can be a bit misleading in its presentation of the investigation of crime, the administration of the law and the legality of evidence that is allowed in the given court of law. Most crimes do not take an hour to solve and reach the sentencing stage of the process, in most cases it can take months, if not years, to be fully investigated, presented to the courts, and justice handed down. Evidence Law, is exactly what it sounds like, it is the rules that help determine what evidence is admissible in a given case, for example, the details of a similar crime committed prior to the current could be perceived as bias against the accused and may not reflect their guilt in the present case or, for example, hearsay, essentially what someone says another party has said., and whether or not that testimony is relevant (Cornell University Law School, 2015). Psychology is a relatively new field of medicine. It was not until the late 1800s that people began studying the behaviors of people as matter of body chemistry and brain activity, prior deviant and violent criminal behaviors were attributed either to religious afflictions, like possession, or to possible disease or base insanity. Since its inception psychology has always faced criticism and questions regarding its legitimacy as a scientific branch relevant to the human condition (Grubin, 2010). The standard argument being that the understanding of human behavior and the human brain is still being understood and new discoveries are being made every day, but it remains questionable because it is not infallible.


That said the psychology of criminal behavior has also faced validity issues and remain questionable as actual evidence in a given case, which means that the evidentiary value of both the polygraph and profiling remain questionable (Grubin, 2010).This remains true, despite the number of cases, where an inadmissible polygraph determined the accused was, in fact, deceiving the court or the number of times that profiling has contributed to the tracking and capture of many incredibly dangerous sex offenders and murderers. In order to understand the history, applications and value as evidence of both lie detection and psychological profiling is to discuss these two psychologically based evidentiary sources individually.

Polygraph or Lie Detector Testing

Determining whether a person is being honest or not has always been difficult to determine, a good liar can be very convincing. In the past, law enforcement and the court would have to make determinations of people’s honesty based upon their visual behaviors and how they react and respond to the line of questioning. People who are lying, due to fear or guilt, sometimes change physically while lying. Bad liars have many “tells” that cue the interrogator that this person is being dishonest. Of course, these decisions are being made by the court and are really a matter of observation and opinion. The first polygraph machines appeared in the early 1900s in the United States, designed by William Marston, who under a pen name was the creative mind behind the superhero character Wonder Woman, who possessed a magic lasso that forced people to tell the truth (Grubin, 2010).It was in the late 1930s that a the more modern machine was introduced that tracked the accused for changes in how they sweat and how their heart rate changed to determine whether or not the person was being evasive or deceptive in relation to the crime committed. Up until 1993 polygraphs were completely inadmissible in courtrooms across the United States, but some states, in certain cases, have allowed the results of polygraph exams to be relevant to the case presented. California, Florida, Georgia and Nevada do allow the exams in certain cases, however in states like New York and Pennsylvania are absolutely opposed to their inclusion as court evidence, however, they sometimes acknowledge their value as a means to gain probable cause against a possible criminal and obtain a search warrant (LaMance, 2015).
Lie detection through the use of a polygraph machine, through laboratory experimentation and practical application, have determined that polygraphs are accurate at a rate of approximately 81% to 91% on a scale of 0 to 100. Supporters of the polygraph argue that given that these percentages are well above 50/50, that this rises above the mathematical chances of coincidence and validates the greater likelihood of accuracy over inaccuracy. This, of course, does not mean that they are, again, infallible. The greatest questions with supporting the accuracy are that, as yet, researchers are not entirely certain why in some cases the liar is not identified. This likely has more to say about the person being questioned and not the test or its application. There are some people who can lie freely without any tells or physiological changes. This can happen because the person genuinely believes the lie to be truth, that the person is practicing some kind of “countermeasures” that will interfere with the ability of the machine to make an accurate determination. In other cases truth tellers may read as deceptive even when they are being completely honest. This can occur when the questioned are highly nervous. The rise in their blood pressure and heart rate could be perceived as deception when , in fact, they are simply nervous displaying nervous energy at being tested not due to guilt of a crime (Grubin, 2010).
There are many people who are opposed to the value of and admissibility of polygraph results as evidence in any American court of law. They feel that psychology is barely perceived as science in many circles, even today, and that polygraphy is a subset and pseudoscience. It is not wise or logical to include the data of an uncertain science in order to determine ones truth or lies in the commission of a crime. They argue that polygraph exams are perceived as a sign of potential guilt from the start. If someone has been asked to take a lie detector test, their honesty in already in question and their guilt more probable; this makes the polygraph automatically biased against the tested. After all, it is a lie detector test, not a truth telling examination (Ebisike, 2007). They also dispute the percentages of their accuracy. They argue that the studies conducted are not an accurate gauging of the real life criminal cases. The researchers used mock crimes, where the “perpetrators” were expected to lie in order to determine the validity of their guilt. These studies may be flawed because these pretend “criminals” were not facing any real legal consequences for their lies or fake crime, therefore their physical state, physiological reactions and psychological disposition may be entirely different from real criminals (Maschke & Scalabrini, 2005). This makes the relevance of polygraph results and court evidence remains questionable and primarily inadmissible. As far as the opposition is concerned that is a good thing.

Criminal Profiling

What is criminal profiling? Profiling combines psychology and investigative tools to determine and predict the behaviors of criminals based on those who have committed the same crimes in the past. They use these comparisons to determine the type of person, their look, behavior, and potential future behaviors to narrow down the list of suspects to specific person based on the profile (Torres, Boccaccin & Miller, 2006). The use of psychology to track and capture criminals based on the pattern of criminal behavior and physical evidence provided is not really a new concept. Profiling is generally reserved for the most serious of offenders, like serial murders or dangerous pedophiles (Ebisike, 2007). They make their determinations based upon the suspect’s behaviors at four different phases in the process of crime.
Antecedent: Was there a vision of the crime that the perpetrator had and what caused them to commit the crime, particularly murder, on one occasion but not in another (Winerman, 2004)?
Method & Manner: Why the perpetrator chose the victim that they chose and what means did they use to commit the crime, stabbing, shooting, or strangulation for example (Winerman, 2004)?
Disposal of Body: How did the perpetrator eliminate the body. Did the murderer kill and leave the body in one location or was it moved from one place to another (Winerman, 2004)?
Post-Offense Behavior: Many mass and serial murderers have strangely after committing their crime, even going so far as to try to interject themselves into the case for example (Winernman, 2004)?
However, it was not until the mid 1990s that people began to want to know more about the people who commit the most heinous and deviant of crimes. The release of the film “Silence of the Lambs,” starring Anthony Hopkins as the fictional serial killer Hannibal Lector and Jodie Foster as Clarice Starling a fledgling FBI profiler. It was the first time the mass public was exposed to the psyche of the truly different and depraved. The long running “Criminal Minds” television series presents complex killers with serious mental problems and outlines the reasoning behind their actions from a psychological perspective with 100% accuracy and success in finding the suspect. This may be a bit misleading. Despite what television and film would have audiences believe, there are not bundles of these teams of profilers that are working cases every single day. In fact, according to experts, that there are less than 20 working profilers, whose case involvements have been contributory, whose profiles can be most trusted, and the profiling evidence found would be the only that could be most trusted in the court of law. (Wagner, 2006).
In the cases where profiling has been absolutely beneficial they contributed to eliminating from the public some of the most mentally ill, psychologically warped and dangerous individuals of modern history. Serial murderers like John Wayne Gacy who murdered and buried, at least, 33 young men, burying the bulk under his home and Ted Bundy who was convicted of committing the murders of 35 women, all of which resembled the girlfriend who left him. Aileen Wournos, an abused prostitute, murdered seven men to maintain and care for her much younger girlfriend. Profilers contributed to the identifying and capture of the disturbing cannibal, Jeffrey Dahmer, who raped, murder and dismembered young men and boys; the remains of some of his victims were found in his refrigerator when he was taken into custody (Hendricks, 2012). Despite their successes criminal profiling remains questionable evidence in the court of law. Much like polygraph examinations, the profile is considered contributory in helping to guide the case and help provide probable cause to focus on certain likely suspects.
The opposition to the inclusion of criminal profiling as evidence in the court of law argues that profiling is too general and not specific enough. It sets a precedent that all suspects are more likely to be guilty because another individual in a similar situation was, absolutely, guilty. This can be problematic ethically, while the bulk of criminal profiling focuses on psychological principles, it can also be turned to other types of crime and suspects and that can become a problem. Racial profiling uses the past crimes of members of a given racial group as a standard to judge every member of that race (Ebisike, 2007). For example, the Arizona law that allows police to question the citizenship of anyone who “suspiciously” looks like they may not be. In other words, anyone who is of a Hispanic/Latino background is probably illegal because most people of that racial group are not in this country legally. This is, of course, completely false and is not beneficial at all in successfully solving real crime. However, this is not a standard of profiling failing to do its job, but a misuse of the science behind profiling which has been incredibly beneficial in many cases even if their evidence is not admissible.
The reality is that science and technology are being innovated every day, the human understanding of human behavior continues to expand and science mover leaps and bounds on what seems a daily basis. Leaning the nature of fingerprints revolutionized criminal investigation and provided from evidence of the presence of the perpetrator at the scene of the crime. DNA has changed the guilt and innocence of any situation for all time. Polygraphs testing and the inclusion of criminal profiling can be bolstered by continuing research and progressive advances that can confirm the value of lie detection and profiling in many sorts of cases as admissible evidence. Already, there have been scientific research that is validating that under and MRI examination there are distinct changes in the brain chemistry of many people when they lie or feel guilt (Langleben & Campbell Moriarty, 2013). Also, they are verifying that some people’s brains, particularly those of serial killers, that function differently than normal brains under the same circumstances. That said it means that the behaviors and deviant thought processes of many criminals may be abnormal and only the proper understanding of psychology and how to apply those principles to criminal behavior will these individuals ever be found and stopped.
The purpose of collecting evidence is to be able to determine what occurred in a location accurately and match that physical evidence to the stories provided by those involved, both victims and perpetrators. The evidence that is admissible in court is relevant depending on what side of the argument you are one. The prosecution will support the evidence that infers the defendant’s guilt, while the defense needs to create reasonable doubt in favor of their client. What is most important of course is that justice is served and the right person is caught and convicted of the crime that they committed; no more, no less. That said polygraph tests may not always absolutely accurate and there may be instances when some people are able outsmart the equipment and it may be, in some cases, imperfect. However, the contributions of lie detector to point investigators in the right direction and aid in these cases help to solve these cases cannot be ignored or underestimated. As the science becomes more and more advanced, it is only a matter of time before America will see polygraph examination as admissible evidence in the future. A for profiling, it remains a relevant in the breaking down of the personality and behavioral triggers of very dangerous individuals with the potential of committing heinous crimes like torture, sexual assault, child molestation or murder. If it had not been for the profiles presented in these cases then law enforcement may never have apprehended the perpetrator (Schurman-Kauflin, 2014). A prime example, again, is Ted Bundy. He was charismatic, handsome, by some standards, and most certainly, did not come across to people as a mentally ill, sadistic, or dangerous individual. The exterior did not fit the inside in this case and that is why profiles were so beneficial. Sociopaths and psychopaths do not process emotions the same, or, in some cases, do not possess compassion and emotions at all (Hendricks, 2012). How much more damage and how many more lives would have been taken had profilers not participated in this case. Like polygraphy, the benefit and advantages of including profiler’ opinions within admissible court evidence are advantageous and are a benefit to seeing the right the criminals is convicted.


We live in a diverse world where many people do things for many different reasons, some of them noble and others entirely nefarious. Understanding those differences and protecting honest participants from those that commit crimes against them is imperative and the basis of laws and courts to begin with. However, as complex as the American court system has become, polygraph examinations and profiling tactics remain inadmissible in all American courtrooms at the federal level and in most courtrooms at the state levels and they may be two of the greatest allies of achieving successful identification, conviction and incarceration of the criminals who commit these crimes. In the end, no one is insinuating that polygraph are flawless or that profilers cannot make mistakes, but their contributions have been incredible in the past and the number of times that have been accurate should outweigh the errors that have ever been made. Ultimately, polygraphs and profiling remain the two very important elements in using a wrong-doers own physiology and psychology against them and aid in making certain they face proper consequences, regardless of whether or not they are admissible in a court.


Ebisike, N. (2007). The use of offender profiling evidence in criminal cases. Golden Gate University School of Law, 1-338. Retrieved from
Grubin, D. (2010). The polygraph and forensic psychiatry. The Journal of the American Academy of Psychiatry and the Law, 28(4), 446-451.
Hendricks, D. (2012, April 25). 7 crimes that were solved with forensic psychology. Retrieved from http://piccano.com/7-crimes-that-were-solved-with-forensic-psychology/
LaMance, K. (2015). Admissability of polygraph tests in court. Legal Match, 1. Retrieved from http://www.legalmatch.com/law-library/article/admissability-of-polygraph-tests-in-court.html
Langleben, D. D., & Campbell Moriarty, J. (2013). Using brain imaging for lie detection: Where science, law and research policy collide. Psychol Public Policy Law, 19(2), 222–234. .
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Schurman-Kauflin , D. (2014, February 11). Does criminal profiling work?. Psychology Today, 1. Retrieved from https://www.psychologytoday.com/blog/disturbed/201402/does-criminal-profiling-work
Torres, A. N., Boccaccin, M. T., & Miller, H. A. (2006). Perceptions of the validity and utility of criminal profiling among forensic psychologists and psychiatrists. Professional Psychology: Research and Practice, 37(1), 51–58.
Winerman, L. (2004). Criminal profiling: the reality behind the myth. American Pscyhological Association: The Monitor, 1.
Wagner, D. (2006, August 24). Criminal profiling 'between science and art'. U.S.A. Today, 1. Retrieved from http://usatoday30.usatoday.com/news/nation/2006-08-24-criminal-profiling_x.htm
Cornell University Law School. (2015). Evidence. Retrieved from https://www.law.cornell.edu/wex/evidence

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