A persons DNA is the same in every cell throughout the body, for example, the DNA found in a persons blood will be the same DNA found in semen, fingernails, or saliva. Because everyone’s DNA is unique it makes it a powerful tool in linking a suspect to a crime or eliminating a suspect. DNA testing can also determine if the DNA is wildlife. DNA can be found in blood, semen, teeth, hair, saliva, fingernails, urine, feces, skin cells, and can be found anywhere in the body. The process of DNA testing begins when a forensic technician gathers blood, saliva, hair, or semen or any other DNA evidence from a crime scene.
DNA has also been extracted from sweat, skin cells, eyeglasses, and used envelope seals. Blood and sperm cells are rich in DNA which makes it very useful in murder and rape cases. The chain of custody is used when collecting evidence; it is a record of individuals who have handled the evidence. Every person who has had physical possession of the evidence, documents everything that happened with the evidence while in their custody. The fewer people in the chain of custody the better, because it reduces the risk of the evidence becoming contaminated.
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Once the DNA has been collected law enforcement can test a suspect’s DNA to the DNA left at the crime scene to determine whether the suspect can be placed at the scene of the crime. There are many different types of DNA Testing; the most common are Polymerase Chain Reaction Analysis (PCR), Short Tandem Repeat (STR), Mitochondrial DNA Analysis (mtDNA) and Y-chromosome Analysis. In the Polymerase Chain Reaction (PCR) Analysis the test reproduces the cells in the sample to duplicate until there are enough cells to conduct a DNA test, this test is ideal when there is a only a small sample of DNA.
The Short Tandem Repeat (STR) test is used to evaluate specific regions within the DNA; the FBI uses a set of 13 specific STR regions that can be used to distinguish one DNA profile from another DNA profile, for the CODIS database to match up individuals to the DNA. Mitochondrial DNA (mrDNA) Analysis is used mostly to test hair, bones, and teeth. Y-Chromosome Analysis is used for tracing relationships among males, such as paternity test or analyzing evidence involving multiple male contributors. There’s a variety of errors that can occur when handling DNA.
The DNA sample can become contaminated when pathogens such as bacteria, viruses or another persons DNA comes in contact with the sample. It can also be contaminated by cleaning fluids, such as detergents. Laboratory equipment such as gels or a DNA probe used in the test may be contaminated, which may cause the results to become fuzzy or blurred. DNA profiles can be entered into CODIS, (Combined DNA Index System) which is a national DNA electronic database of DNA profiles used to identify suspects. CODIS allows laboratories throughout the nation to share and compare DNA information.
Although a major part of matching DNA is computerized, a technician makes the final determination that there is a match in DNA. There have been thousands of hits, and have provided breaks in numerous cases, even cold cases. There are many unsolved cases that could be solved through the advancements in DNA technology, such as murder, rape, even burglary. Police investigators have started using DNA technology for nonviolent crimes such as burglaries, and car thefts, which were previously ignored because they did not produce enough DNA like blood or semen.
New highly sensitive crime labs can create a genetic profile using only 6 cells worth of DNA, compared to the 150 cells needed for more common DNA testing. In all fifty states DNA is collected from convicted sex offenders, and some states collect DNA for other violent crime offenders. Other than solving criminal cases DNA can also help solve missing person cases, victim identification in mass disasters, and unidentified remains. There are roughly 40,000 people every year who go unidentified, through DNA technology they can take samples from bones or teeth depending on the decomposition of the body, and match the DNA.
The Missing Persons DNA Program stores DNA profiles made up of DNA from relatives of a missing person, and DNA samples from the unidentified missing person. DNA can also be used to establish innocence. DNA technology has resulted in the exoneration of numerous death row inmates over the past decades, a trend that will continue. The Innocence Project has proved through DNA testing that 238 inmates did not commit the crime they were accused of. The advanced DNA technology makes it possible to obtain results that have been previously tested but were incomplete, or did not have DNA testing was not available at the time of the crime.
Post conviction testing can only be requested if there has been never been any DNA testing. Kirk Noble Bloodsworth was convicted of rape and murder of a nine year old girl; he spent eleven years in prison, two of those years on death row. He became the first person who was exonerated through DNA testing. DNA is a relatively new procedure that revolutionized criminal investigations. It has become the most effective tool in identifying missing persons, proving innocence or guilt, and solving many different types of crimes. DNA technology is always advancing and will continue to impact forensic science.
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