When we use GC-MS for forensic science purposes for controlled substance detection, we can basically divide the world into two camps. First, is the world of solid drug dose in pre-consumption form. The second is in the world post-consumption form analysis in a biological matrix (blood, urine, or oral fluid) which is otherwise known as […]
The importance of t0 in forensic chromatography
If you are bored and want to have a little fun, call up your local crime laboratory, ask for someone who preforms their chromatography (it doesn’t matter if it is liquid chromatography or gas chromatography). When you get that person ask them a simple question: What’s the t0 (pronounced “t subzero”) for your method that […]
Why per se Driving Under the Influence of Drug Based Prosecution is Not Scientific and How Probation Violations for Marijuana Use May Be Wrong
I cannot imagine that a single rational and sane person cares for drug impaired drivers to be on the road among us driving what amounts to a guided missile weighing about 3,000 to 5,500 pounds or more. As has been shown time and again, a drug intoxicated driver can be a weapon of mass destruction. […]
Zero is not a valid data point for calibration purposes
When the quantitative measurement really matters to determine guilt, we have to understand how that measurement is achieved. In the case of the analysis of biological samples that are tested, quantitation of an unknown is derived from a calibration curve. The proper construction of the calibration curve is a crucial component of quality control. It […]
The myth of the neutral scientist doing forensic science
One of the most ridiculous claims that I hear in court is a claim by a forensic technician or expert witness (regardless of what particular discipline he or she is from) that somehow he or she is a neutral and detached scientist doing science, and therefore he or she has no bias whatsoever. This total […]
Guest Blog Post From Dr. Frederic Whitehurst PhD JD: On sampling when testing multiple packets
Sampling Crime: On sampling when testing multiple packets By: Frederic Whitehurst, J.D., Ph.D. [1] If we accept that forensic crime laboratories are completely overwhelmed, understaffed, underequipped, and exhausting environments in which to function, we see reality. Despite political rhetoric to the contrary, there has been little, if any, relief for those folks in crime labs […]
Quality Control in GC-FID: Teaching the machine right from wrong
It is shocking but very true statement that most sophisticated instruments such as a Gas Chromatograph (GC) with various detectors whether it is a mass spectrometer (MS) or flame ionization detector (FID) when produced and manufactured are incapable of producing meaningful results “straight out of the box.” These machines have to be “taught” what it […]
Guest Blog Post From Dr. Frederic Whitehurst PhD JD: Mr. Fletcher vs. Mr. Daubert A Journey into the Surreal
Mr. Fletcher vs. Mr. Daubert: A Journey into the Surreal By: Frederic Whitehurst, J.D., Ph.D. Many a defense attorney has looked in amazement at the courtroom “identification” of Cannabis Sativa L. by a law enforcement officer sporting a gilded pot metal badge and a high school diploma who has written a report that would […]
The myth of specific identification of Marijuana in criminal court Part 2: How is most marijuana testing conducted in the United States?
In 2006, more than 829,000 people were arrested in this country for marijuana-related offenses alone. Since 1937 with the passage and adoption of the Marihuana Tax Act, marijuana has been effectively prohibited in the United States. Literally millions upon millions of people have been accused of possessing marijuana. The question becomes are these convictions scientifically […]
First, let’s educate all of the lawyers
The great Bard once penned: All: God save your majesty! Cade: I thank you, good people—there shall be no money; all shall eat and drink on my score, and I will apparel them all in one livery, that they may agree like brothers, and worship me their lord. Dick: The first thing we do, let’s […]
How the GC-FID arrives at a quantitative result: Auto-integration versus Manual Integration
A frequently asked question on the listservs that I belong to basically asks the following question: In GC-FID use to quantify Blood Alcohol Content where EtOH is the target analyte, how does the machine arrive at the reported number? The machine is called a Gas Chromatograph with a Flame Ionization Detector (GC-FID). Typically the sample […]
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