Conclusive Results Help Make the Case in Forensic Toxicology

Scientific investigation of crime has become a highly visible topic in North America and elsewhere. It's in news reports about untimely deaths caused by the use of illicit drugs or the abuse of prescription medications. It's also the centerpiece of popular television shows such as The New Detectives and CSI: Crime Scene Investigation that dramatize the investigative processes and procedures of forensic science.

Beyond the headlines and dramatizations, forensic science is the application of science to legal matters. Law enforcement agencies use it to help identify perpetrators, test for intoxication and more. When fatalities occur, medical examiners and coroners use forensic methods to identify victims and determine the cause and manner of death. Because the findings may be used as evidence in legal proceedings—to help convict the guilty, exonerate the innocent, settle an insurance claim, or pinpoint the cause of death—the results must be conclusive.

Testing for the presence of toxins

Forensic toxicology is a specialized branch of forensic science that focuses on the identification and measurement of toxins in the human body. In a criminal or death investigation, toxicology is used to prove the presence or absence of alcohol, drugs or other toxins in a person's blood, urine or vitreous eye fluid. All detected substances must also be quantified such that a toxicologist, coroner or medical examiner can determine the likely effects of those substances in the human body.

Advances in measurement technology have improved the conclusiveness of test results, but this has in turn increased the demand for testing. As a result, forensic laboratories often face a large backlog of work and sometimes take three to six weeks to provide test results. Fortunately, new analytical techniques can help reduce the backlog and ensure faster delivery of conclusive results.

Sending samples to the lab

In the United States, forensic labs are generally operated by state or federal agencies. These labs typically perform tests for commonly used drugs and medications. There are also private, independent labs that are staffed and equipped to help handle not only the backlog of common tests but also perform complex, cutting-edge methods that identify rare toxins and new or unusual drugs.

National Medical Services (NMS) of Willow Grove, Pennsylvania, is one such lab. Since 1970, NMS has built a reputation for providing very thorough analyses and for performing esoteric tests that are inherently difficult and demanding. As an example, if a medical examiner (ME) has reason to believe someone died from eating toxic mushrooms, the testing itself can be very difficult and the ability to produce conclusive findings depends on having a toxicology database that includes the unusual compounds found in poisonous fungi. In such a case, the ME would send a sample to the local state lab, which might forward it to NMS for specialized testing. NMS would send its results back to the state lab, which would evaluate the report and in turn forward the results to the ME.

To continue meeting the demands of peer and legal scrutiny while also setting higher standards of test quality, NMS is always striving to develop new methods that facilitate the more difficult tests. That's one reason NMS has adopted the retention time locking (RTL) capability available with certain gas chromatography and mass spectroscopy (GC/MS) systems from Agilent Technologies.

Screening more samples in less time

Retention time is the fundamental qualitative measurement of chromatography. Most compounds are identified by comparing the retention time of an unknown peak to that of a standard.

"We live and die by retention time when we do gas or liquid chromatography," says Fran Diamond, a senior scientist at NMS. "Retention time of a compound provides preliminary identification and the mass spectrum provides conclusive identification."

NMS uses the Agilent 5973Network GC/MS system with the MSD Productivity ChemStation software, running the Drug Data Analysis and Enhanced Data Analysis modes.

It's much easier to identify peaks and validate methods if there is no variation in the retention time of each analyte. RTL can reduce the time and complexity often associated with routine chromatographic maintenance. It allows methods to be transferred between equivalent GC/MS systems without time-intensive edits to the quantitative database and reacquisition of standards. RTL can also improve productivity for most applications by reducing the time and set-point changes required to update a method.

To cope with the growing demand for testing, saving absolute time is another benefit of RTL. "We typically handle 50 to 100 cases per day," says Diamond. "Without RTL and GC/MS, our analysts would spend more time on the data than it took to acquire it." What's more, when an analyst looks across multiple chromatograms, viewing spectra and comparing peaks, RTL also reduces the possibility of overlooking a compound that may be masked by an interferent.

Catching the little things

NMS has compiled an extensive reference database of nearly 300 toxicological compounds (which it has generously made available for download from Agilent's user-contributed library). Every time NMS runs a panel it adds any new drugs that show up, and it's adding new entries to the database literally every day.

The RTL screener handles the formerly manual process of searching the database. It automatically finds and highlights the major or unusual hits so the analyst can go back and take a closer look at the most important peaks. "With the screener database," says Diamond, "you click 'go' in the evening and the next morning the results for dozens of samples are ready for the analysts to view."

As you might imagine, NMS has been involved in some high-profile cases. Adds Diamond: "RTL is part of our total process. Although it hasn't yet provided make-or-break discoveries, it certainly helps us catch the little things that other methods might miss."

For more information

Agilent GC/MSD systems and RTL capabilities provide powerful solutions that can help forensic toxicology labs accelerate the process of delivering conclusive results. To learn more about these and other Agilent chemical analysis products and resources, please visit the main page of the Life Sciences/Chemical Analysis section of our Web site.