Analyzing the Causes of Accidents and Deaths

Alumna Mackenzie Dunn is a toxicologist with the Bexar County Medical Examiner's Office.
Alumna Mackenzie Dunn is a toxicologist with the Bexar County Medical Examiner's Office.

At the Bexar County Medical Examiner’s Office, Mackenzie (Willis) Dunn helps investigate how people die or whether an accident was caused by drunk or drugged driving.

As a toxicology chemist, it is her job to determine if drugs, alcohol, poison or other chemicals led to deaths or accidents by analyzing samples in the laboratory.

“I have been here a year and eight months,” said Dunn, a 2012 Master of Forensic Science graduate. “I love it. I really enjoy it. It’s always very interesting and always changes. You see something new all the time.”

HandThe Bexar County Medical Examiner’s Office, located in San Antonio, investigates between 2,500 to 3,000 cases a year of people who die suddenly, violently or unexpectedly to determine the cause and manner of the death. They also analyze blood samples in cases of intoxicated manslaughter or assault.

When medical examiners perform autopsies, they also collect samples that are sent to the lab for analysis, looking for clues to manner of death, which may include homicide, suicide, accident or natural causes.

Bexar County also has a no refusal policy for suspected drunken driving, which means if a suspect refuses to take a Breathalyzer test, the police agency will get a search warrant from a judge for a blood draw. All cases of intoxicated manslaughter and assault are sent to the lab for evaluation.
Unlike the popular CSI series where cases are solved in an hour, samples in real life may take weeks – if not months—to process for unknown substances.

Dunn uses state of the art equipment at the Bexar County Medical Examiner's Office.
Dunn uses state of the art equipment at the Bexar County Medical Examiner's Office.
“One test can take up to a week to get results,” said Dunn. “We do multiple tests on a sample. It can take a month for a sample without drugs or alcohol and several months if drugs or alcohol are detected.”

The Bexar County Medical Examiner’s Office is only one of about 30 institutions in the United States and Canada accredited by the American Board of Forensic Toxicology. It currently has about 10 toxicologists on staff and offers state-of-the-art technology, such as Gas Chromatography-Mass Spectrometry (GC-MS), Gas Chromatography Flame Ionization Detector (GC-FID), and Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS).

A group of illegal drugs.The instruments are used to detect drugs, alcohol or other chemicals in a variety of bodily fluids or tissues, including blood, urine, vitreous, bile, muscle, liver or kidney. The toxicology test turns up a large variety of substances, including meth- amphetamines, cocaine, marijuana, allergy and sleeping medications, hydrocodone, oxycodone and other prescription drugs.

While heroin is also another common substance found in toxicological tests, in Bexar County, it is more likely to be black tar heroin because of the city’s proximity to the Mexican border, Dunn said.

“It is crazy what people will take, but it makes our jobs more interesting,” said Dunn.

Dunn posed with faculty and fellow forensic science students from SHSU.
Dunn posed with faculty and fellow forensic science students from SHSU.
Dunn said that “everything” in the program at Sam Houston State University helped prepare her for work in a toxicology lab, including the repeated warning about the paperwork involved. Occasionally, chemists are also called to court to testify, although it has not happened to Dunn -- yet. Generally, the medical examiner will testify about the lab findings, but chemists may be called on to address the instruments and testing procedures used.

“Everything they told us was right,” said Dunn of SHSU program. “If you think it is always fun and exciting, it’s not. We kill lots of trees. There is a lot of paperwork.”

Dunn said the hands-on experiments at SHSU really made a difference. At the Department of Forensic Science, students spent a full year in research, designing and testing experiments, which is essentially what she does on a daily basis for her job.

“The two years in the MSFS program prepared me the best that I could have been when I got to the hands-on work,” said Dunn.

Member of The Texas State University System