Answer

DNA Profiling

                  DNA profiling is a forensic analysis method that is used in criminal investigations by which an individual’s specific DNA pattern is obtained from a body tissue. The DNA pattern after identification is then compared with the DNA pattern of DNA samples obtained from a crime scene. If there is a match, then the individual is assumed to have been involved in the crime. It is also used in parentage testing and genealogical and medical search (De Moor, Vander Beken, & Van Daele, 2017).

Processes for Avoiding Contamination of DNA Samples

            DNA samples can only be relied on as evidence in court if handled and tested properly. The method by which scientists take a small sample of DNA and study it by amplifying it to a large amount it is called    polymerase chain reaction (PCR). To ensure DNA is not contaminated the first step is to ensure areas for sample preparation are designated and prepared early in advance.  Separate bench tops should be set up to avoid contamination from other DNA amplifications done previously (McGlynn, 2019). The second step is ensuring all equipment used in the PCR are kept in the PCR set up area. This avoids contamination. The third process is storing reagents to be used for the PCR in a separate place.  This assist in ensuring DNA samples are not contaminated. The fourth method is by using separate equipment and tools such glove boxes, waste baskets, pipettes and lab coats among others for the pre-PCR and post-PCR processes. This ensures DNA amplification for old cases does not contaminate the DNA sample being analyzed (McGlynn, 2019).

 The fifth method is using reaction mixture separation dedicated for a DNA sample alone as well as pipettes and pipette tips with aerosol filters dedicated to a specific DNA sample.  The next one is ensuring reagents, pipettes and equipment used in Post-PCR process are not also used in Pre-PCR process. Analysts should also not take note books, biro pens and other items used in Post-PCR to Pre-PCR process i.e. items for each process should be labeled and used separately to avoid contamination of the DNA sample (De Moor et al, 2017). Lastly, the scientists should ensure that PCR cycles are kept to a minimum to avoid contamination as many cycles are prone to contamination.   In addition, DNA samples should be dried before they are packed and steps should be used to ensure analysts do not mix their DNA with samples collected in the field by using gloves, face masks and other protective gear. These items should also be changed regularly (De Moor et al, 2017).    DNA analysts should ensure proper transportation and storage of the samples by keeping the evidence dry by use of paper bags and tightly sealed containers (McGlynn, 2019).

Contamination Issues in DNA testing

       The risk of contamination of DNA at a crime scene before collection is one of the most significant issues in DNA profiling. People could intentionally or unintentionally contaminate DNA samples at a crime scene.  Other natural factors like heat or moisture could contaminate DNA samples hence making them useless (Garrett, 2017). Contamination at the PCR laboratory where amplification of small DNA samples is done is also a major issue. Scientists could unintentionally mix pre-PCR reagents, equipment, tools and chemicals with Post –PCR reagents, tools and equipment which would lead to contamination of DNA samples (De Moor et al, 2017). 

The next issue is carrying out too many PCR cycles which would lead to contamination. The next issue is contaminating DNA samples at the laboratory with old DNA samples used for other purposes.  If proper separation of equipment and chemicals, cleaning, gloves etc. of one DNA testing is not done properly contamination can occur (De Moor et al, 2017).

Court cases where decisions were influenced by DNA contamination

A case where DNA evidence was contaminated and which led to the release of the accused persons was in the case held in an Italian court in 2007. This case involved the murder of Meredith Kercher; a British student. In this case the accused were Raffaele Sollecito and Amanda Knox.    DNA analysis on samples collected at the crime scene was declared to have been contaminated (De Moor et al., 2017).  The two accused were acquitted by the court. The next case involved Michael Morton who was sent to jail for killing his wife.  After spending many years in jail, there was DNA testing on appeal which exonerated him of the crime and he was subsequently released (De Moor et al, 2017).

My take on the two cases discussed above

Ruling in the Meredith Kercher case accepted the validity of DNA evidence and ruled out the results as inadmissible. This is because the DNA found in the object of murder was contaminated. The DNA samples could have been contaminated in the laboratory or during collection the crime scene (De Moor et al, 2017). The second case of Michael Morton was also a case that involved DNA contamination. DNA samples were collected from the bedroom of Michael Morton and contamination could have occurred when the forensic analysts were collecting DNA sample at the crime scene (Garrett, 2017).

The importance of DNA evidence in determining the outcome of cases in court

Forensic evidence can influence court judgements especially in murder cases, burglary, rape and arson cases among others. Most of these crimes involve bodily contact between the victim and the perpetrator. For example, in a rape and murder case the victim may deposit semen in the victim’s body (Garrett, 2017). Since the victim is not able to identify the perpetrator, DNA analysis on body fluids in the victim can be retrieved and analyzed. Using DNA profiling, the perpetrator can be identified, located and arrested. However, it is very important that DNA profiling is done carefully to avoid contamination which makes the DNA evidence inadequate and may even lead to conviction of an innocent person (Garrett, 2017).