DNA Profiling and its Relevance in Criminal Investigation

DNA profiling is a technique that allows one to identify a person at the molecular level. Over recent years the use of DNA evidence in criminal investigations has increased. DNA testing has helped to classify offenders with poor enforcement and solve complicated cases such as rape, murder, and murder after rape, etc. The ability of DNA typing has made immigration issues and complex paternity tests possible when the father is not available. Rapid identification of individuals in mass tragedy (man-made explosions) using DNA typing was also possible.

In some nations, computerized DNA databases were developed to classify convicted offenders. DNA is an effective forensic device since no two individuals have the same DNA except identical twins. In other words, the sequence or order of the DNA building blocks in a particular region of the cell is different making the DNA of each individual is unique. No doubt, in criminal investigation cases such as murder, rape, disputed paternity, man-made disaster, etc., DNA is of great significance, but there are no clear rules under the Indian Evidence Act,1872 and the Code of Criminal Procedure,1973 to handle forensic science matters.

This article discusses the science of detection of DNA and its application in forensic investigations and criminal prosecutions, including criminal charges, appeals, and prosecution following conviction. This outlines the key benefits and costs of increasing the role of recognition of DNA in the criminal justice system with a special focus for India. It is believed that DNA technology can address problems in the future.


The scientists Francis H. C. Crick and James D. Watson first identified DNA (Deoxyribonucleic acid), also called the building block or genetic blueprint of life, in 1953. Crick and Watson identified DNA’s double-helix structure, which resembles a twisted ladder, and defined the function of DNA as the material that makes up the living organism’s genetic code. The pattern of the compounds which constitute the DNA of an individual life-form determines the growth of that life-form. DNA is the same across an individual’s body in any cell, whether it is a skin cell, sperm cell, or blood cell. No two people have the same DNA code, except for identical twins.

During a forensic investigative DNA analysis, using highly advanced laboratory instruments, a suspect’s DNA molecule is disassembled first, and selected fragments are separated and measured. The DNA profile of the perpetrator is then matched with one derived from a sample of physical evidence to see whether the two fit. Where there is a definitive non-match, the defendant may be disqualified from consideration. If a match happens, a statistical analysis is conducted to assess the possibility that the sample of physical evidence originated from another individual with the same DNA profile as the suspects. Juries use this statistical test to determine whether a suspect is guilty or innocent.

Legal Definition of DNA

The strong and contentious study of deoxyribonucleic acid, or DNA, the substance that makes up the genetic code of most species, is among the many modern methods that research has developed for the study of forensic evidence. DNA analysis, also called DNA typing or DNA profiling, analyses DNA present in physical samples such as blood, hair, and semen and decides whether it can be compared to DNA extracted from different individuals. For criminal trials, the study of DNA has become a standard form of evidence. It is also used in civil litigation, particularly in cases where the Paternity of Identity is determined.

Interpreting DNA Analysis findings in criminal investigation

  1. Inclusion: When a known person’s DNA profile (victim or suspect) matches the crime scene evidence DNA profile, that person is “included” as a potential source of that evidence.
  2. Exclusion: If an individual’s DNA profile (victim or suspect) does not fit the DNA profile produced from the evidence on the crime scene, the referenced person is “excluded” as the provider of the evidence.
  3. Inconclusive: Inconclusive results suggest that DNA testing did not yield information that would permit the inclusion or exclusion of a person as the source of biological evidence.

Questions concerning DNA analysis among ordinary people

  1. If I am being investigated for a crime by the police, is the police entitled to order me to provide a DNA sample for their criminal investigation?
  2. If a member of a family commits a crime, will his DNA at the crime scene lead law enforcement to falsely believe I committed the crime? How similar is DNA between members of the family?
  3. What steps would I take if I suspect that police unintentionally contaminated DNA evidence found at a crime scene during the collection process?

The relevance of DNA evidence in Criminal Investigation

In recent years in India, the use of DNA as evidence in criminal investigations has increased. DNA research has aided law enforcement, identified criminals, and solved serious crimes. On the other hand, DNA evidence has shown that many accused persons are in fact innocent.

In criminal cases, DNA profiling has helped not only to crack cold cases and connect crimes with criminals but in many cases has also helped to locate victims. In certain cases, the victims are being assassinated with a general viewpoint of hiding the criminal identity and it is impossible to associate recovered body remains with the victim due to long-lasting investigation procedures.

DNA profiling in such cases is proving to be a bane. It also assists in further proving the accused’s guilt or innocence, but tampering with the DNA evidence may lead the case in the wrong direction as a result of which courts are left with no other option other than to give the accused the benefit of the doubt. The case of Santosh Kumar Singh v State via CBI also known as the Priyadarshini Mattoo case was an excellent example of this.

Tampering evidence along with shoddy investigation was the main obstacle the prosecution faced in the courtroom. The clincher was that the DNA test confirmed rape, but again during the investigation, it was being tampered with, which provides an advantage of the accused’s circumstance of doubt. Amid multiple facts in support of the prosecution, the Trial Court acquitted the accused by arguing that CBI had failed on several counts, including hiding from the court that the evidence obtained by the accused was produced on behalf of the accused. Even an appropriate procedure for performing the DNA test, depriving the court of an opportunity to judicially review it.

The courts cannot afford to grant the judgments based on ethical and moral grounds, but the basis should be solely legal in character and undoubtedly lose its originality after being tampered, resulting in incomplete justice.

Limitations of DNA testing

The implementation of DNA profiling has raised some significant challenges to an individual’s legal rights such as the right to privacy and the right to self-incrimination, which is why the courts often rejected it as evidence. Furthermore, the admissibility of the DNA evidence before the court is often based on its correct and proper compilation, preservation, and documentation that can reassure the court that the evidence before it is credible.

In India, there is no clear legislation that can provide the investigative agencies and the court with certain guidelines, and the procedure to be followed in cases involving DNA as its evidence. However, certain laws authorize medical professionals to examine the person accused of rape and the rape victim’s medical evaluation respectively, but the admissibility of these facts remained questionable as the Supreme Court’s opinion and various High Courts remained contradictory in different decisions.

Judges do not question the scientific precision and conclusiveness of DNA testing, but in certain cases, on the grounds of legal or constitutional prohibition and often public policy, they do not accept these facts.

In Rajiv Singh v. The State of Bihar, the Patna high court referred to OJ Simpson’s case and noted the potential errors involved in the DNA process at different stages and observed:

One of the enduring consequences of the case of OJ Simpson is likely to be increased examination of forensic DNA evidence provided in criminal trials by defense lawyers. The defendant, in effect, put the crime laboratory on trial in the Simpson case.

There is no major dispute about the underlying scientific concepts in DNA profiling, but the adequacy of laboratory procedures and the expertise of the testifying experts should remain subject to investigation. While there is general agreement within the scientific community that DNA profiling will produce results with very high probability, it is not without problems that the complex DNA profiling technique. Mistakes and incorrect handling of the DNA-sample will produce false findings at any point of the seven-step process, which in some cases can lead to a life sentence or even a death penalty verdict.

Hence, the adequacy of laboratory procedures and the expertise of the testifying experts should remain subject to investigation. Biological evidence gathering is of critical importance in forensic science. Sample manipulations or contamination, whether knowingly or negligently, could vitiate the expert report.


It can be concluded from the study that the Supreme Court has yet to focus on the constitutional validity of different forensic instruments to discover the facts during the investigation, while there have been several cases whose prosecution and innocence have been centered on DNA evidence. In order to make the DNA profiling technology more effective, the legislature and the court must come up with certain recommendations or regulations so that the investigation can be less botched and so are the chances of miscarriage of justice.


Q1. What is DNA?

A1. DNA is a chemical that exists within the body of each cell. The DNA is stored in 22 pairs of structures known as chromosomes, shaped like an X, plus an extra pair-the sex chromosomes-that decide whether someone is male or female. Women have two X chromosomes in this final pair while men have one X chromosome and one Y chromosome. — chromosome is composed of two long strings of chemical letters, twisted together in the popular double helix form. On this twisted chemical ladder, the chemical letters exist in pairs as rungs. The genetic code’s four chemical letters spell out instructions to the cell on how to create the proteins that enable the human body to develop and function normally. The DNA sequence parts which contain the protein-making instructions are known as genes. The whole sequence is called a genome.

Q2. What is a forensic DNA profile?

A2. A profile of a DNA is a number string based on sections of a person’s DNA. Short strings of the chemical letters constituting the DNA of an individual occur frequently in sections of the genome. They are called short tandem repeats (STRs). The number of repeats varies and can be counted between individuals. The numbers of STRs used in a forensic DNA profile differ in various countries. Each STR consists of two strands, one inherited from the mother and one from the father, so there are 26 numbers recorded in the US and 20 numbers recorded from the number of repeats at each STR in the UK. Also included in the DNA profile is a gene test called amelogenin that can be used to determine whether the DNA sample comes from a male (with an X and Y chromosome) or a female (with two X chromosomes). A DNA profile is not special but it is thought to be very remote, less than one in a billion, the likelihood of two complete forensic DNA profiles matching wrongly by chance. The likelihood of a fake match depends on the method used for profiling.

Q3. What happens when the police take a person’s DNA?

A3. A medical professional or a police officer can take a person’s DNA, depending on the country and the circumstances. Medical practitioners are able to obtain blood samples and ‘intimate samples’ from a person’s private body parts. Typically, the police collect saliva samples using a mouth swab. In certain nations, such as the UK, police are permitted to use “reasonable force” to take DNA from a person who has declined to provide a sample. Typically, that means cutting out any strands of their hair. Details such as the name of an individual, alleged crime, date of birth, appearance, and address, or ID number will also be registered, so police can have a record of their DNA sample. A barcode is typically used to connect the sample to the personal record.

Q4. How does DNA help to solve crimes?

A4. People at a crime scene will leave traces of their DNA because it is inside every cell of their body. To acquire a forensic DNA profile, DNA can be collected from the blood, semen, saliva, or hair roots left at a crime scene. This can be matched with identified suspects’ DNA profiles for the crime, or with other individual DNA profiles stored on a DNA database. A match between the DNA profile of the crime scene and the DNA profile of the suspect suggests they were at the scene of the crime. The importance of this evidence in solving the crime may vary: DNA on a cigarette ass may have been dropped earlier in the day or planted by someone who wanted to involve an innocent person in the crime; on the other hand, a woman who has been raped could have had DNA in semen that indicates that a specific man was or was not likely to be involved. But even a rape case may not be straightforward: for instance, if the man insists that the woman chooses to have sex.

Q5. What are the questions about human rights in DNA databases?

A5. Since DNA is left everywhere a person goes, DNA databases may be used to track individuals and their families, even if no crime has been committed. For example, if their DNA profiles are stored on a computer database, DNA collected from coffee cups at a political meeting can be used to track the people who were there and identify their relatives. Anyone who infiltrates the system can also be vulnerable to harassment by a DNA database and can also be used to identify victims, including children. DNA evidence is not foolproof and evidence of DNA can be planted to attempt to involve an individual in a crime. Errors and failures can also occur like laboratory mix-ups. DNA databases may also be biased by holding profiles of people predominantly from ethnic minority communities. If records of arrests are kept, connected to a person’s DNA, these can be used to deny employment or visas to individuals, even if they have never been convicted of a crime. Therefore, provisions are required to protect human rights, thus allowing for the use of DNA in criminal investigations.


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