DNA In Crime Scene Investigation

This paper explores deoxyribonucleic acid (DNA) collection and its relationship to solving crimes. The collection of DNA is one of the most important steps in identifying a suspect in a crime. DNA evidence can either convict or exonerate an individual of a crime. Furthermore, the accuracy of forensic identification of evidence has the possibility of leaving biased effects on a juror (Carrell, Krauss, Liberman, Miethe, 2008). This paper examines Carrells et al’s research along with three other research articles to review how DNA is collected, the effects that is has on a juror and the pros and cons of DNA collection in the Forensic Science and Criminal Justice community.

DNA forensics is a division of forensic science that focuses on the use of genetic material in criminal investigation to answer questions pertaining to legal situations, including criminal and civil cases. Through DNA testing, law enforcement officers are able to identify human remains or the individual responsible for a crime. DNA testing is a highly advanced scientific process that involves replicating the human DNA sequence to create a genetic map of an individual. Because of its reliability, DNA testing has become a significant factor in criminal cases. However, it has also been identified as having the potential to violate privacy and constitutional rights. The DNA identification process consists of five stages. These five stages

From cases such as OJ Simpson to Chandra Levy, DNA profiling also called DNA fingerprinting or DNA typing has played a major role in the criminal justice system. The law enforcement community uses DNA profiling to rule out or identify suspects. Unlike hair microscopy, bite mark comparisons, shoe print comparisons, and firearm tool mark analysis, DNA typing has been developed through massive scientific research and has undergone meticulous scientific evaluation (Innocence Project). DNA is a foolproof method of identifying a perpetrator of a crime.

I. Before the 1980’s, courts relied on testimony and eyewitness accounts as a main source of evidence. Notoriously unreliable, these techniques have since faded away to the stunning reliability of DNA forensics.

The Australian Institute of Criminology has produced documentations explaining “the technique of ‘DNA identification’ compares the DNA of two bodily samples to ascertain whether or not they came from the same human being. Identity of DNA in the cells across both samples implies that the samples are derived from the same person (or identical twins); non-identity implies different human sources.”

DNA testing is a critical and accurate tool in linking accused and even convicted criminals for crimes, and should be widely used to assess guilt or innocence before jail sentences are imposed. It was started up by scientists Francis C. Crick and James D, Watson in 1953 as they had described the uses, structures and purpose of the DNA “deoxyribonucleic acid” genetic fingerprint that contains organism information about an individual (testing

Today in the crime world, DNA evidence is strongly accepted in solving crime cases. This is all based in part by allowing a crime laboratory to have a designated unit whose main goal is to analyze DNA evidence to aid investigators with positive outcomes in crime case solving. With that being said we are going to discuss the functions of a DNA unit within a crime lab as well as address the vital role these units play in solving crime.

Due to the uniqueness of DNA it has become a powerful tool in criminal investigations

No two people, except identical twins, have identical DNA sequences, which makes DNA testing appealing to law enforcement. Two types of DNA testing include short tandem repeat and variable number tandem repeat. Short tandem repeat requires less DNA compared to variable tandem repeat, which is “useful when a sample has been degraded at the crime scene.” (“DNA Evidence”) Whilst DNA evidence is a useful weapon in solving crimes, it is not infallible; therefore, it needs to be used with caution, especially with partial DNA profile,

DNA forensics can also narrow down suspect pools, exonerate innocent suspects, and link crimes together if the same DNA is found at both scenes. However, without existing suspects, a DNA profile cannot direct an investigation because current knowledge of genotype-phenotype relation is too vague for DNA phenotyping. For example, a profile from a first time offender that has no match in any database may give the information that the criminal is a left handed male of medium stature with red hair and freckles. It would be impossible to interview every man who fits that description. However, with available suspects, DNA forensics has many advantages over other forms of evidence. One is the longevity of DNA. Although it will deteriorate if exposed to sunlight, it can remain intact for centuries under proper conditions (Sachs, 2004). Because DNA is so durable, investigators can reopen old cases to reexamine evidence.

DNA technology has been used as a means to identify perpetrators of rapes and murders with a very high degree of reliability. However, interpretation of the evidence can be problematic at times. This problem comes into play when there are mixed sample’s, partial profiles and with contamination of the evidence submitted. Mixed samples

With regard to the US, where social science and STS research have, focused less on forensic databases and more on the production of expertise and evidence in court, Jay Aronson provided a historical account of the early practices, the scientific and legal controversies, and the ultimately successful acceptance of forensic DNA evidence in court in 2007. Another particularity of social science and STS research in this domain is that it has so far mostly concentrated its “high end” forensic technologies, namely those which received a lot of public attention because they were new, because stakeholders in the criminal justice system struggled to determine the parameters of scientific reliability and admissibility, or because they were prominently featured in the media. While the use of DNA analysis for police investigations and forensic casework dates back to the late 1980s, the second half of the 1990s marked the beginning of the quest to render DNA profiles systematically and routinely searchable and minable by setting up centralized DNA databases in many countries around the world. A DNA molecule is a long, twisting chain known as a double helix. DNA looks pretty complex, but it's really made of only four nucleotides: Adenine, Cytosine, Guanine, and Thymine. These nucleotides exist as base pairs that link together like a ladder. Adenine and Thymine always bond together as a pair, and Cytosine and Guanine bond together as a pair.

Law Enforcement keep notes on arrests that have founded people innocent of crimes, and retention of an innocent person's DNA can be charge or otherwise, seen as a invasion of that person’s privacy and civil liberties. Dr. Alec Jeffrey, a former professor at the University of Leicester laboratory, consulted with his lawyers to develop the new type of technique called DNA profiling. His technique would prove that DNA fingerprinting (profiling) can individualize evidence compared to the blood typing. DNA profiling compares 13 standard STRs to form a profile. The analysis used by the scientists, uses PCR and STRs to profile an individual. It is highly unlike that two individuals’ identical numbers of repeats for all 13 STRs, will match, which DNA fails is hardly never due to a successful match of 385 million to 1. This makes DNA profiling the most accurate tool in Forensics.

Every State in the Nation has a DNA database that allows for the collection of DNA profiles from offenders convicted of particular crimes. CODIS software enables State, local, and national law enforcement crime laboratories to compare DNA profiles electronically, thereby linking serial crimes to each other and identifying suspects by matching DNA profiles from crime scenes with profiles from convicted offenders. The success of CODIS is demonstrated by the thousands of matches that have linked serial cases to each other and cases that have been solved by matching crime scene evidence to known convicted offenders.

DNA fingerprinting is a technique that is used to determine how likely it is whether genetic material came from a specific person or family group. Since 99% of human DNA is identical, that means that it is only 1% of our DNA which is different, and it is that 1% that we look at when we are attempting to determine the origin of a DNA sample.