Solving Crimes with DNA

DNA (deoxyribonucleic acid) is a hereditary material present in each cell of the body including the drop of blood, saliva, flakes of skin, everything contains DNA which can be used for a person’s identification on the basis of their unique genetic make-up. Globally, prosecutors and police departments use DNA as an evidence to identify victims and link criminals to the crimes they have committed. Forensic scientists can compare the samples of DNA taken from suspects to the DNA found at the crime scene.

Where Does DNA Hide

   The following items may contain DNA material: clothing, underclothes, secrets, masks, hats, Gloves, weapons, tools, bedding, sexual assault evidence kits, Toothpicks, fingernail scrapings, toothbrush, eyeglasses, stamps or envelopes, ligatures, condoms, cups/bottles, etc. With technological advancements, forensics scientists use smallest biological samples to analyze and develop DNA profile. Skin cells can be obtained from an object touched by a person which is considered as a low-level DNA or touch DNA. It can be collected from the victim’s skin or bruises where they were treated roughly. Low-level DNA is important when retrieving a fingerprint is not possible.

Victim Identification

In many cases, DNA testing is one of the best methods to identify a victim or victims. To identify the remains of a victim, DNA from the remains found at the crime scene/ accident site must be matched to DNA from the victim or the victim’s relatives. By obtaining the complete and accurate information about the victim, the process of identification becomes easier. It includes dental records, unique physical characteristics, etc. This information is considered prior to DNA testing. For the successful testing, remains are compared with the sample collected from the relatives of the victim. Therefore, it is necessary to collect DNA samples from family members, personal items, and prior medical specimens of the victim if the victim has gone through diagnostic test/procedure and the medical specimen is present at the hospital. Medical specimens include biopsy sample, bone marrow donor sample, newborn screen bloodspot, etc. Personal items include toothbrush and hairbrush. Close relatives include brother or sister of victim, biological parents of victim and children of victim. Other relatives include maternal relatives which are aunts, cousins, uncles, half-brothers, or half-sisters on the victim’s mother side. The most useful DNA sources are medical specimens and personal items. Close relatives are considered useful whereas other relatives are less useful source of DNA because they cannot provide information on the genetic identity of the victim. Teeth is considered as one of the important DNA source since it does not get affected from extreme environmental conditions and is resistant to postpartum degradation.

 DNA profiling is the most reliable and efficient way of identifying bodies and separated body parts in case of disasters and mass casualties. In such case, post-mortem DNA samples are collected from bone, teeth, muscle, and bone marrow with the minimal risk of contamination.

Suspect Identification

DNA is also a powerful investigative tool in identifying the suspect in criminal cases. DNA collected from the site can either eliminate a suspect or can be linked to a suspect. During sexual assault, evidence like blood, skin cells, hair and semen can be taken from the victim’s body or from the crime scene. The samples are then compared with the suspects. DNA profile collected from the site can be entered into CODIS if no suspect exists in order to locate the suspect in any part of the United States and for linking serial crimes. These evidence are linked to other crime scenes by using DNA databases by entering the suspect’s sample of DNA into DNA database. If the suspect commits the same sexual assault after a few years and it is proved through the analysis of biological evidence, the suspect would be sentenced for his second crime and would be prevented from committing other crimes during the period of his incarceration.

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