forensic pathology

forensic pathology

Human identification testing is used primarily to verify paternity in cases of dispute, match forensic samples to suspects and to identify human remains.

The first step in the process of human identification testing is the collection of biological material from a crime scene or paternity investigation. Following collection, DNA is extracted from the biological source material. While most commonly blood is tested, DNA has been successfully extracted by the lab from biological source material such as saliva, buccal swabs, nails, sperm, bone fragments, teeth, cigarette butts, etc.

Specific DNA regions scattered throughout the human genome are targeted and copied by means of PCR. These regions are typically located between genes and vary in size from person to person. Commercial kits are commonly used to enable PCR of these regions. AMPATH utilizes the kit developed by The Promega Corporation that permits the amplification of 27 regions or STR markers.

The STR alleles are interpreted following separation by size using capillary electrophoresis on an ABI3500 Genetic Analyser and data analysis software. A statistical interpretation then assesses the rarity of the alleles from the resulting DNA profile. Subsequent to the DNA testing, a written report is created summarizing the work conducted and the result obtained.

DNA analysis always requires a comparison between at least 2 samples: in forensics a questioned sample and a known sample and in paternity testing an alleged father is compared to a child. The results are either an inclusion, an exclusion or inconclusive.

In the case of human identification, testing chain-of-custody refers to sample collection, consent, transport, analysis and reporting of results. To satisfy the legal requirements for paternity testing, all tested parties have to be properly identified and their samples collected by a professional who is not related to any of the tested parties and has no interest in the outcome of the test. At AMPATH, DNA tests can generate legally admissible results and expert witness testimony is available should it be required.

AMPATH is SANAS accredited to perform these tests and laboratory audits are performed annually to evaluate the entire operation of the laboratory.

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Forensic Pathology

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