04,June 2024
To all the questions that are not answerable in the general investigation, there is a solution called DNA Analysis. Whenever the crime investigators are not able to get the answer for the evidence they have collected from a crime scene, they use the sure-shot technique of DNA examination. Earlier this field was not much liked by the police department, but over the years it has earned the faith of such investigators for providing the most reliable results. A few years back, people used to hesitate to provide their DNA samples for the purpose of investigation due to several myths spread in society. However, now that all such myths and misconceptions are cleared people are getting more literate and are considering the relevance of DNA analysis in forensic investigations. Here in this blog, we have given the complete details on the evolution of DNA in forensic crime investigations.
What is DNA?
Deoxyribonucleic Acid, commonly known as DNA is an important unit of the human body that contains genetic programs of an individual. These programs are coded by special chemical compounds known as bases. These bases are Guanine, Cytosine, Thymine, and Adenine which are typically arranged in long sequences. The basic building blocks of life that are known as codons are groups of three bases. Genetically relevant information represents 10% of the human genome that is subject to evolutionary pressure that affects the development of organisms.
What is DNA Analysis in Forensics?
DNA Analysis is the process of examining, analyzing, and evaluating the genetic materials of a biological sample collected from a crime scene as evidence. The final results of these examinations help in identifying the actual identity of the victim, offender, or the people associated with the criminal investigation in any manner. It uses scientific techniques to analyze the samples like blood, tissue, hair, bones, saliva, semen, etc. Tests that can be performed for analysis of DNA samples are DNA sequencing, polymerase chain reaction, short tandem repeat analysis, etc.
Evolution of DNA Analysis in Forensic Investigation:
The first ever evidence of using DNA identification in forensics can be traced to 1986 when UK police used DNA traces to verify the suspect’s confession in a case where he was held accountable for the rape and murder of two innocent people. However, later based on the findings of the tests it was clear that the suspect was not the actual offender. But instead of this method being scientific in nature, the DNA evidence collected from the crime site or the offender was not allowed to be submitted as authentic evidence in a court of law. Here we have given the complete details on how DNA analysis was introduced in the field of forensics and how it has reached its current status:
1. Introduction of DNA Examination in Forensics:
With the advancement in technology and facilities available for the analysis, the technique of DNA analysis has progressed over the years. In comparison to earlier time periods, this technique provides more and better information within less duration than too with less available material for the purpose of examination.
After the analysis of the samples collected, the experts create a profile of the person to whom this DNA belongs. This profiling is known as Forensic DNA profiling which was introduced in the mid-1980s and used to be known as “DNA Fingerprinting”.
2. Challenges Faced For DNA Analysis Acceptance:
Initially, DNA profiling was not considered strong enough to be presented as evidence in a court of law. It was because such evidence was subjective in terms of scientific interpretation and the reports thus presented were prepared on the basis of probability and not on confirmed findings.
However, this method of DNA analysis became prominent in the 1990s and thus was widely accepted as evidence. The radical change in acceptance of DNA profiling as evidence from being considered an unauthentic and reliable source to being considered a golden standard in crime investigation has seen a remarkable evolution in the field of forensic science.
3. Evolution of Use of Body Fluids in DNA Analysis:
The presence of body fluids at the crime scenes is not a unique thing. This is because they are found easily at any crime site and thus can be used as evidence in crime investigations. The most common evidence found in criminal activities is saliva which can be easily collected from bitemarks, water glasses, tissue papers used, etc.
Even the collection of this kind of evidence is the easiest one since it can be collected using vials, oral rinses, swabs, and cytobrushes. Saliva is genetically analyzed using the method of hybridization, PCR method, SNP genome typing, DNA sequencing, along with other methods. Over the years, the technique has become faster, and easier to perform, with less expenditure incurred for the examination that too without hampering the results.
4. Use of Ancient DNA in Forensics Evolution:
The amount of DNA content that is found in ancient DNA evidence is comparatively lower in quantity as compared to modern samples. Therefore to get the best use out of such samples it is advised that they are collected with utmost accuracy thus reducing the chances of DNA loss.
Importance of DNA Analysis in Forensics:
The relevance of DNA in forensic analysis has grown to another level. It is because of its strong use in the identification of a criminal, victim, or suspect by using DNA markers, statistical analysis, and the present records in databases. It enhances the information gathering and identification of species ability thus helping in case solving. The unique ability of DNA technology to be used as an identification tool has led to tremendous success in case solving and thus efficiently delivers justice to the victims.
DNA Analysts use this technique for the following purposes:
- Identify criminal,
- Determine the parentage,
- Identification of people who died in an accident,
- Establish relationship status, etc.
Methods used in DNA analysis:
In the collection, analysis, and examination of the DNA samples, several important methods are used. Some of the most important methods used in DNA analysis are given below:
- Hybridization,
- PCR based analysis,
- SNP genotyping,
- DNA sequencing,
- DNA micro-array techniques,
- Spectrophotometry,
- Microsatellite markers,
- Genotyping with different loci,
- Single nucleotide polymorphism,
- Short Tandem Repeat,
- Variable Number Tandem Repeat (VNTR),
- High-resolution melting,
- Amplified Fragment Length Polymorphism,
- Gene sequencing,
- ABO blood typing,
- Iso-enzyme typing.
How is DNA Analysis Used in Forensics?
The incredible power of DNA technology as an identification tool has brought a tremendous change in the criminal justice system. The database of DNA consists of the relevant records with short tandem repeat (STR) DNA markers. The use of DNA identification has completely revolutionized the crime detection field. This domain of forensic science is highly reliable in increasing the conviction rate. Here we have given the complete details on how the analysis is done:
1. Restriction Fragment Length Polymorphisms (RFLP) Method:
The technique in which genomic DNA is analyzed with enzymes that cut DNA with each specific occurring sequence of bases and create fragments of DNA is known as RFLP. Changes in the DNA of an individual cause the loss of one or more sites and sometimes variation in fragment lengths.
2. Variable Number of Tandem Repeat Sequences Typing:
Repeated short sequences of DNA in tandem are present in the stretches of the human genome. The pair of these sequences repeats in a given sphere and are highly variable in nature. The repeated sequence of DNA is known as the Variable Number of Tandem Repeat Sequences. These are characterized into mini and micro satellites depending on the size of blocks that are repeated.
3. Polymerase Chain Reaction:
One of the most interesting facts about DNA is that they are degraded rapidly once they are no longer present inside a living organism. PCR enables unlimited amplification of minute DNA traces that may be found in small dry samples of bone or skin.
4. Short Tandem Repeat (STR):
STR commonly known as Short Tandem Repeat is polymorphic in nature and their alleles are differentiated by the repeated sequence copies within their locus. With a greater number of STR being used in typing their discrimination value increase. The Short Tandem Repeat that is chosen for typing contains tetranucleotide sequences of discrete sizes.
DNA Analysis plays an important role in today’s crime investigation procedures. From the day of not being officially accepted as a reliable source of evidence presented in a court of law, it has grown to another successful level of worldwide acceptance of standard DNA evidence. It is considered to be a most precise test and its results are trusted by all involved organizations and justice delivery systems because these findings are not because of the facts present in the books instead their result is the actual outcome of the test findings. Since this field is able to answer all those questions of forensic crime investigation that can’t be answered easily by other domains, it is widely accepted and the first preference of the investigators. If you are someone who wishes to serve society by reducing the crime rate by helping to increase the conviction rate then this is the field for you.
References:
- https://www.discovermagazine .com/the-sciences/the-evolution -of-dna-forensics-and-its-impact -on-solving-crimes
- https://www.frontiersin.org /articles/10.3389/fevo.2021 .646130/full
- https://www.ncbi.nlm.nih .gov/pmc/articles/PMC3561883/