COMPROMISED DNA EVIDENCES- AN INSIGHT

The emergence of evidence of DNA (deoxyribonucleic acid) is one of the best examples of how technology has changed the situation in criminal justice, especially to immunize those who have been falsely convicted. DNA evidence narrows down to several possibilities within the human population, rather than technically identifying a single suspect. However, as long as it is properly processed and analyzed, it is very accurate and useful. Read to know more about how the?DNA evidence works and how it affects you and your loved ones.

WHAT IS DNA?

DNA is a basic component of life. The information encoded in the DNA of an organism serves as a blueprint for the biological development and function of the organism. DNA is present in the cells of all living organisms, and by testing the DNA found in human cells, scientists can create a DNA profile for that person. Studies suggest that forensic DNA analysis is about 95 percent accurate, although only one-tenth of human DNA varies from individual to individual and estimates vary.

HOW IS DNA SOURCED AND ANALYZED?

Researchers can collect DNA from a variety of sources. Not all samples contain enough DNA to enable DNA profiling, but almost all biological evidence can contain DNA. It includes teeth, bones, soft tissues, saliva, blood, semen, hair, and even synovial fluid. Forensic researchers analyze biological samples to obtain the DNA profile of the person from whom the sample came from. If the investigator is already targeting the suspect, we can collect a sample for comparison with the evidence collected at the crime scene. There is also a database of DNA profiles that researchers can use to identify suspects by comparing database information with DNA profiles obtained from?biological evidence.

THE DEVELOPMENT OF FORENSIC DNA EVIDENCE

DNA profiling of individuals was not in existence, however, until the mid-1980s, when Dr. Alec Jeffrey, an English scientist discovered that a pattern was repeated over and over in certain sections of the DNA strand. The number of these repetitions varies between individuals (except for identical twins, who have the exact same DNA).

Dr. Jeffrey developed a test to measure the variation in the length of these repetitions. With the help of this test, he was able to identify individuals by comparing samples of their DNA. This test is later on known as restriction fragment length polymorphism (RFLP). RFLP is an accurate and reliable test, but it requires a relatively large amount of DNA to perform on. Nowadays Laboratories use tests based on the polymerase chain reaction (PCR) method, which helps in the testing of a very scarce amount of DNA extracted from biological samples.

ACCURACY OF DNA EVIDENCE

?DNA evidence is very accurate, assuming that researchers properly collect and process biological evidence and that forensic scientists perform the analysis correctly using accepted methods. The probability that one person's DNA profile will match another person's DNA profile is very low, with some estimates about one-billionth. Although both have inherent flaws and inaccuracies when compared to fingerprints and witness testimony, DNA evidence is a very effective means of matching suspects with biological samples collected during criminal investigations. Because of its accuracy, criminal defense lawyers are increasingly relying on this type of evidence to prove the accused's guilt or innocence. This type of evidence has also blamed people through post-conviction analysis of biological samples. In the absence of DNA analysis until recently, a review of the evidence collected in previous investigations shows that the DNA profile of a person convicted of a crime matches the DNA profile of a biological sample collected at the crime scene.

WHY PROPER DNA EVIDENCE COLLECTION IS SO VITAL?

There are rules that must be followed and SOPs that must be operated for any type of evidence to be submitted. The collection and preservation of DNA evidence must be done by the book. Collecting fingerprints, hair, and fibers; and swabbing for fluids like blood, semen, and saliva is only successful when great care is taken to prevent contamination or mishandling. The power of DNA as a tool for convicting criminals and exempting falsely accused is indisputable. However, proper DNA collection, handling, packaging, and transportation is required to obtain court-acceptable evidence. DNA, once compromised, does not stand up in court, even in the strongest matches.

WHAT IS COMPROMISED DNA EVIDENCE?

Since its introduction in the 1980s, DNA typing of biological evidence has played a central role in forensic medicine. This technology works with the CODIS network and the implementation of national standards for the DNA database of convicted criminals. It provides law enforcement agencies with a very effective way to resolve violent crimes across the country. In addition, DNA evidence has led to the immunity of many falsely convicted people. Current forensic DNA technology requires 0.2-2.0 Nanograms of double-stranded DNA with a length of at least 100-500 base pairs. However, many evidence samples do not meet these minimum requirements because the target DNA is exposed to an environment where widespread DNA damage can occur. Forms of DNA damage are mainly Oxidation, Hydrolysis, pyrimidine dimer, cytosine deamination, and DNA-DNA and DNA- protein cross-linkages. This damage reduces the size of the target DNA and can be too small for the polymerase to amplify. Chain reaction (PCR) in the typing protocol, and some forms of damage, resulting in modification of the nucleotide bases that block PCR amplification. Since DNA samples commonly found in crime scenes show varying degrees of damage, the effectiveness of DNA typing techniques is limited by the condition of the sample and there is currently no way around to tackle this problem. The use of DNA typing can be extended to law enforcement and social interests if a treatment is found that improves the condition of the degraded sample without affecting the genetic profile of the DNA trace. Forensic scientists cannot always afford the abundance of high-quality DNA evidence. Traces of DNA are often exposed to the environment for different periods of time, and in some situations, decades can go from committing a crime to collecting and analyzing evidence. Sample DNA can be damaged by a variety of natural and unnatural processes. And this deterioration in sample quality makes it difficult, if not, impossible to obtain genotypes.

IS THERE A WAY TO RECOVER COMPROMISED DNA EVIDENCE?

Currently, there are no ways to restore heavily damaged DNA for genotyping. There were some attempts seen where researchers tried to facilitate STR DNA genotyping from the heavily degraded DNA evidence in which two approaches have been taken –

1. They had attempted to add extracts from highly repaired proficient bacteria to extensively -degraded biological evidence in the belief that they can improve the Quality of a large enough fraction of the target DNA in the sample to facilitate STR genotyping.

2. They developed a method that allowed them to capture and concentrate the targets of STR genotyping. In this method intact short tandem repeats could be recovered from highly degraded forensic DNA samples.

However, these methods failed. Failure to provide DNA evidence will have serious consequences. Criminal cases will remain unresolved, uncaptured perpetrators continue to cause injury and harm to the community, investigations will be expanded, and trials that could have been prevented or at least shortened, due to lack of DNA evidence they will be extended erroneously. Falsely Convicted individuals remain imprisoned. Victims and the criminal justice system will suffer at a great cost to society.

If only these methods would have been successful or in the future, if there will be enhancements in the methods described above, it may be possible to selectively detect specific DNA sequences within forensic DNA samples and obtain DNA evidence samples that are quantitatively and qualitatively suitable for PCR-based genotyping.

?If successful, this method :

(A) Allows accurate amplification of STR loci in digested DNA samples.

?(B) Prevents changes in the STR repeat length of the DNA sample to be analyzed.

(C) Prevent further deterioration or damage to the DNA sample to be analyzed. The availability of this technique should expand the options of forensic scientists and improve their ability to accurately genotype samples endangered by DNA degradation.

CONCLUSION

Forensic DNA Samples that are compromised cannot be restored to date. There are no methods to restore these compromised samples. The research is still going on to find a suitable method to tackle this problem. Till then, the only thing we can do is to collect and preserve the DNA evidence very carefully to prevent contamination and mishandling. And take enough precaution so the violation of the chain of custody can never occur. If police personnel cannot account for a piece of evidence at some point between collection at the Crime scene and presentation at the trial - the court could say the evidence has been compromised. DNA evidence won't hold up in the court of justice if it's been compromised- not even the strongest match! Always remember that DNA does more than just identify the source of the Sample, it can also place an individual at a crime scene, a place where the person claimed not to have been. There may be someone's life at stake. It can refute a claim of self-defense and put a weapon in the suspect's hands. It can change a story from an alibi to one of consent. The more we know how to use DNA, the more powerful tool it becomes!

Article By- Pratima Kumari

Source- Science Hub, Science Direct

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