DNA technology and forensics

DNA is used for identification in forensic science.

DNA can be used to identify any type of living organism. This is done by analyzing DNA sequences that are unique to a species. The field of forensic science uses DNA analysis to identify individuals. While it is not yet possible to identify individuals by exact DNA matches, it is possible to analyze DNA regions that give a very high probability for matching the individual with the sample.

Identification

Only a minute fraction of DNA differs from one person to the next and forensic scientists can analyze these differences to create a match with samples of hair, skin, or bodily fluids. When this process is done, it creates what is called a DNA fingerprint. There is a very low probability of the DNA fingerprint being the same for two individuals, so a reliable match can be made.

Function

Forensic science uses DNA technology for a number of purposes. One of the most well known is to match DNA with a physical sample left at a crime scene to identify criminal suspects. This may be used to establish guilt or to exonerate someone wrongly accused of a crime. DNA can also be used to identify victims of a catastrophe. The science of DNA analysis can establish family relationships or determine the pedigree of livestock. It has even been used to identify the authenticity of consumables such as expensive wine or caviar.

Process

To create a DNA fingerprint, two samples must be compared to one another. In criminal cases, the forensic scientist will take a sample from a suspect and analyze it for the presence of a certain set of DNA markers. This is done by designating small pieces of DNA called probes that seek out and bind to a complementary sequence in the sample. A series of probes creates a distinctive pattern for the individual. This data is then compared to a physical sample found at the crime scene. If there is a match, it means there is a very high probability that the suspect contributed to the DNA found at the scene.

Considerations

DNA evidence is not absolute. Forensic scientists scan 13 DNA regions when they establish a DNA fingerprint, and there remains a minute chance that a different individual has the same DNA fingerprint. However, the judicial system has concluded that the probability of error is so small that DNA evidence can be used with high reliability to identify an individual. In fact, DNA evidence is considered more precise in giving a correct identification of an individual than an eyewitness account, where accuracy rates are closer to 50 percent.

Expert insight

According to the Human Genome Project, DNA sequencing technologies will continue to progress. At some point, it will probably be possible to do exact matches of very large DNA segments, and possibly even entire genomes. When this can be done, it will be possible to do precise forensic identification of individuals with no possibility of error.

References

• The Human Genome Project: DNA Forensics
• DNA Initiative: About Forensic DNA