With experience as a forensic pathologist in Austin, Texas, Dr. Danielo Perez has performed autopsies across rural communities in Central Texas that do not have their own medical examiner’s offices. In this capacity, Dr. Danielo Perez performed a number of duties, including toxicological analysis of blood and urine.
When undertaking drug testing among live patients, blood and urine samples are commonly analyzed in the lab. After death, similar tests present a number of challenges, including variable concentrations depending on the area of the body in which the chemical is found. Urine specimens can also be difficult to analyze when decomposition occurs.
While urine may be useful for initial tests, a drug’s presence does not always correlate with drug effects at the time of death. This has to do with the way the body takes an extended period to eliminate drugs and their metabolites through urine. Often, the presence of toxins in a urine sample is used to determine whether liver and stomach contents should be further tested.
Postmortem toxicology testing primarily involves the liver, where a majority of toxins and drugs are metabolized. Even when no traces of substances are found in the blood, they may still be concentrated in the liver (although forensic interpretation is often challenging). Another avenue of postmortem toxicology is the clear, gel-like vitreous humor, which is found in the eye and is particularly useful for determining blood alcohol concentration.