DNA evidence has helped the law enforcement to match perpetrators with the crime scene and are the most useful tool to law enforcement to investigate a certain crime case.
DNA evidence is extracted from its biological sources and then measured to evaluate the quantity of DNA recovered. The DNA is then copied using the polymerase chain reaction(PCR) (1) thus creating enough DNA to enable the analyst to generate a DNA profile(3). DNA sources can vary from the type of DNA markers found.
DNA markers like fingerprints can be derived from objects like knife handle, steering wheel whereas a DNA marker like saliva or teeth mark can be found from gum, popsicle stick and bite marks. This means that everything found on the site of a crime scene can be used or contain evidence that might yield successful DNA profiles of the suspect. Different types of evidence can include or exclude an individual from being involved in the crime.
Usually, DNA can be directly transferred from the suspect and can be deposited on the victim’s body, deposited on an object or deposited at a location and vice versa(1). The evidence found must be carefully collected, preserved, stored and transported prior to any analysis done. DNA evidence, however, is not always correct and can be contaminated. DNA of a person can be transferred to a surface even though the person has never come into contact with it.
This then makes even strong genetic evidence almost insignificant. A witness testimony is made entirely out of how the witness perceives, record and recollect the memory of the crime scene. Eyewitness error, however, is the leading cause of wrongful convictions(4). A memory from the eyewitness can be altered by post-event information that may make the testimony inaccurate resulting in disability of identifying the correct perpetrator(4). A witness testimony can also change during eyewitness interview with law enforcement officers as their memory could be altered when pressurized. Such case where a witness memory has wrongfully identified a criminal from the Bloodsworth case. There were no physical evidence and a confession from Bloodsworth that showed he was the murderer.
However, two children who reported as an eyewitness pointed out independently that Bloodsworth was there at the scene of the crime.Bloodsworth was apprehended due to the similarity of his facial features to the composite given by witness statement and how the two children were able to point him out. In this case, however, some of the description given did not match Bloodsworth as they described the perpetrator to be blonde instead of red-haired and the height given did not match him but due to the testimony given by the two children, he was rendered guilty by the jury. He was however proven not guilty after a DNA evidence of a semen was found during the later stage of investigation on the victim’s panties that proved not be Bloodsworth’s.If I was a jury, I would believe in DNA evidence more as it is a more concrete evidence and due to proper training these days, DNA evidence contamination has a lesser chance of happening. DNA evidence is also more likely to be true as it shows that the person was around due to the DNA present.
Even so, as a jury, I would still take into account the witness testimony and also the plead of the perpetrator to see if it all links. I believe that even with no scientific knowledge, I would still believe in DNA evidence more as from the case study mentioned above, a memory can be skewed and a DNA evidence that was missed out was able to prove that someone was innocent instead.