Forensic science (also known as forensics) can be defined as the use of scientific methods to respond to questions relating to a legal system. The questions could be related to civil action or solving a crime. The term forensics is derived from the Latin word forensic, which means “before the forum”. This word was conjured during Roman times when criminal charges were brought before a group of people in a public forum (Inman & Rudin, 2000). The accused and his accuser would present their speeches and give accounts of their versions of the story. The person who argued his case better than the other determined the outcome.
In the USA, there are more than twelve thousand technicians in the field of Forensic Science. DNA analysis has led to much advancement in the criminal justice system. Many legal practitioners advocate for and support the use of forensic science in solving crimes. It is a significant breakthrough in the field of forensic science that has thoroughly changed the course of investigation.
In ancient times, forensic science had not developed enough to be of much use to criminal investigations. Most crimes were solved through careful thinking and logical reasoning. This changed in the 20th century. Below is a timeline on developmental milestones in forensic science. In the1960s, the first computerized dispatch system was put up in the police department at St. Louis. In 1966, a system for passing messages linking all police computers in every state of America except Hawaii was put in place (Lincoln, 1998). In 1967, the Federal Bureau of Investigations established the National Crime Information Center (NCIC) as the earliest national computing center for law enforcement. NCIC is a computer programmed filing system which keeps track of stolen vehicles, wanted persons, weapons, and other valuable items. In 1968, the number 911 became the official emergency number on which the fire department, the police and ambulances could be reached. In the late 1960s, many attempts were made to come up with technologies that could control riots as alternatives to the use of force. Many gadgets were invented during this period. These include plastic, wooden, and rubber bullets, tranquilizer dart guns, high voltage shock batons, and the taster.
In the 1970s, most police departments in the USA were computerized. They had computerized dispatch systems, systems for the management of information and centralized dispatching systems for the administering of medical, fire and police services for larger areas (Nafte, 2009). In 1972, the National Institute of Justice developed comfortable body armor for the protection of police officers on duty. This armor is said to have saved more than twenty thousand lives since its inception. In the mid 1970s, The National Institute of Justice the assessment of six different devices for night vision. In 1975, Rockwell International put up the first device for reading fingerprints at the FBI. It was put to use in 1979. In 1980, the 911 system was enhanced to allow dispatch to see the address of the person making the emergency call. In 1982 pepper spray was invented as an alternative to force. By 1993, most police departments were computerized. In 1985, DNA testing was done for the first time. In 1996, the National Academy of Sciences officially accepted the use of DNA for evidence and no longer questioned its reliability. This was the birth of DNA forensics.
Since the introduction of DNA testing, biological substances (such as skin, blood, hair and other bodily fluids) have proved to be the most dependable evidence in crime scene investigations. This is especially true for cases dealing with sexual crimes. Deoxyribonucleic acid (DNA) makes up the intricate genetic code that differentiates every person from the next. DNA analysis can tell whether the accused is indeed the culprit if the genetic material found at the crime scene matches his own. Forensic testing is more than 99% accurate, and the proof it gives is irrefutable. This is because a person’s genetic code is unique to them. No two people have the same DNA sequence.
In 1987, a person accused of rape by the name Tommie Lee Andrews was the first human being in America to ever be sentenced based on DNA evidence. He served a prison sentence of 22 years. The following year, a killer nicknamed “South Side Strangler” was given a death sentence after being linked to a number of murders and rapes in Richmond. DNA analysis also led to the sentencing of Gary Ridgeway, also known as the “Green River Killer". He was found guilty of committing many murders in Seattle and its environs during the ‘80s and ‘90s. He was given a sentence of 48 life sentences which were to run consecutively.
DNA analysis has tremendously helped in solving cases by revealing evidence which the investigators may have missed. There are currently more than five million records of convicted criminals through DNA analysis. During the earlier years of DNA testing and analysis, juries were hesitant to pass convictions based on DNA evidence. A good example is the trial of O.J. Simpson. The former football player was acquitted of murder charges due to doubts on the reliability of DNA evidence discovered at the scene of the murder.
DNA analysis has also led to the exoneration of many people by proving their innocence. About two hundred and forty convictions have been reversed in 33 states in America. Seventeen people awaiting execution have been released after being cleared by DNA evidence. Scott Fappiano spent over twenty years in prison for allegedly committing rape before being released in 2003 when DNA evidence proved he could not possibly have been the attacker.
Techniques used for DNA analysis
Restriction Fragment Length Polymorphism
It is a technique used to analyze the varying lengths of fragments of DNA that are the result of digesting a sample of DNA with a certain type of enzyme. It is usually a restriction endonuclease that divides DNA at a particular series pattern which is known as a recognition site. The absence or presence of particular recognition sites in a sample of DNA produces DNA fragments of varying lengths, which are then divided by use of gel electrophoresis. These fragments then undergo hybridization using DNA probes that combine with a corresponding sequence of DNA in the sample. The use of RFLP was one of the precise first practical applications of DNA analysis to the field of forensic investigations (O’Hara & O’Hara, 1994). With time, more efficient DNA analysis techniques have been invented, and RFLP is not commonly used. This is partly because it necessitates the use of a huge amount of DNA. It was also not possible to accurately analyze samples which had been degraded by factors from the environment such as dirt using this technique.
In this technique, polymerase chain reaction (PCR) is a technique used to replicate millions of precise copies of DNA from a single biological sample. This method of amplification of DNA using PCR allows the analysis of DNA on small biological samples. This ability of PCR to increase such minute quantities of DNA makes it possible for even extremely degraded samples to undergo analysis. One must, however, ensure that these samples remain uncontaminated by other biological substances during the processes of collecting, identifying and preservation of materials.
STR Analysis: this is short tandem repeat (STR), which is a technology used to analyze specific regions within the nuclear of a DNA sample. Differences in regions of STR can be used to differentiate a single profile of DNA from another (Inman & Rudin, 2000). The FBI normally uses a set of 13 definite regions of STR on CODIS (Combined DNA Index System), which is a computer program that runs state, local and national databases of profiles of DNA from crime scene evidence that remains unsolved, missing persons and convicted criminals. The probability of two people having 13-loci profile of DNA which is the same is one in a billion.
Mitochondrial DNA Analysis: This analysis (mtDNA) can be used to study DNA from samples that cannot be analyzed using STR or RFLP. Unlike in STR, PCR and RFLP, it is not entirely necessary to extract nuclear samples for analysis. In mtDNA, analysis can be done using other cellular organelle such as the mitochondria. This makes it possible to analyze older materials (Nafte, 2009). This technique is used to solve cases that have remained unsolved for many years.
All biological mothers have the exact same DNA of the mitochondria as their children. This is for the reason that the mitochondrion of the embryo is derived from the cell of the mother’s egg. The sperm of the father contributes to the DNA of the nuclear. Comparing the profile of the mtDNA of the remains of a person can help in the identification of missing persons.
Analysis of the Y-Chromosome: The Y chromosome is on passed straight from the father to son. This makes the analysis of genetic indicators on the Y chromosome extremely useful in paternal testing. This can also be used to solve rape cases.
Theories in Forensic Science
One theory that has contributed to further research and advancement in forensic science is the theory of primary and secondary transfer. Primary transfer refers to the transfer of genetic material from a person to an object. An example of this is when someone touches the door knob and leaves his DNA on it or when a person lies on a bed and leaves strands of hair on it. Secondary transfer occurs when an individual does not make any contact with the object in question, but somehow his DNA ends up on it (Higgins, 2010). Consider the following scenario. Mike walks into a grocery store. A random stranger walks up to him and shakes his hand, only to realize that he had mistaken him for another person. Later that day, the police show up at Mike’s house to arrest him for committing murder in an apartment across the grocery store. His DNA was found on the hammer that was used to kill the victim. Mike claims that he has never been to the said apartment. This is a case of secondary transfer of DNA. The killer got Mike’s DNA when he shook his hand and transferred it onto the hammer when killed the victim. These show that it is possible for DNA to be transferred to an innocent person, which could lead to a wrongful conviction.
Limitations of Data Analysis
In as much as data from DNA analysis is particularly useful for criminal investigations, there are a few limitations. One limitation is that matching DNA materials taken from a crime scene to the DNA sample taken from a suspected criminal does not necessarily guarantee that the suspect is guilty (Wambaugh, 2009). Experts in the field of forensic science deal with probability, which leaves a margin for error. The jury also tends to rely too much on evidence from DNA, and this does not always give the real picture. There could be other explanations as to why the suspect’s DNA was present at the scene of the crime. Relying too much on DNA evidence without giving consideration to any other evidence could lead to a wrong conviction.
There have also been cases of fraud where the actual criminal plants samples at the scene of the crime. This could lead to the incarceration of an innocent person. One such case was seen in 1992, when a Canadian doctor by the name John Schneeberger put false DNA evidence inside his body so as to throw off any suspicions in a rape case.
Another problem with DNA testing is that it takes time, and not all police departments have the necessary equipment. This has led to cases being backlogged in laboratories, which results in many violent offenders being free to commit more crimes. With advances in DNA analysis, most of these challenges could become less intense.
Future expectations of DNA analysis
In the future, it is expected that science and technology will be so highly developed that there will be significant improvements in methods used to collect evidence. This will help in accelerating the process of serving justice. Technological advancements are also expected to simplify the process of analyzing genetic materials as well as lead to lowering of the overall cost of DNA analysis. New genetic tests are also expected to be formulated. These methods will be more accurate and less likely to be degraded of affected by environmental conditions and contaminations (O’Hara & O’Hara, 1994). It is also expected that in future CODIS will be far more advanced and will have significantly improved in its effectiveness. It should also be possible to distinguish with ease between close relatives such as siblings and twins with extremely high accuracy. It is also expected that the primary and secondary theories of transfer will be studied further so as to shed more light on the subject. It is possible that innocent people have been incarcerated due to secondary DNA transfer while the real criminals roam free. Not only will this help in keeping justice, but will also rid society of certain people that have proved to be a menace to society.
The use of DNA profiling in criminal justice is a serious issue facing U.S. courts. Many law practitioners have embraced it as a source of evidence for their cases. This is a major in the right direction field of forensic science that has totally changed the course of investigation. However, DNA analysis raises concerns on privacy issues. Many people believe that crime suspects should reserves the right to refuse to have their DNA samples taken from them. As advances continue to be made in science, DNA analysis is becoming more popular as it becomes more accurate and less costly. It features in television shows and in local drugstores as do-it –yourself paternity testing kits. It has also been used in the identification of human remains, for instance in the September 11th terrorist attacks.
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