* ABC Chicago…

After a months-long investigation, the ABC7 I-Team discovered some test results from a prominent Chicago lab used by prosecutors have been deemed unreliable and could be inaccurate.

The lab, University of Illinois Chicago Analytical Forensic Testing Laboratory, is accused of providing flawed test results in cases of driving-under the influence of marijuana, many of them resulting in motorists convicted and sent to jail, and there are allegations of a cover-up. […]

“The University of Illinois Chicago lab has been providing misleading testimony in court, and as a result of that, their accrediting agency decided to audit the lab and then began to find a series of, they call them, nonconformance or failure to follow scientific standards, which has now put about 1,600 cannabis DUI cases that they tested in jeopardy,” [criminal defense attorney Don Ramsell said]. […]

Emails and internal communications obtained by the I-Team revealed the lab acknowledged testing problems last March and waited until May to alert police departments and prosecutors of possible flawed results. […]

The University of Illinois Chicago has now stopped doing tests for marijuana in law enforcement cases.

Go read the rest.

* Meanwhile, from an Albuquerque, NM publication back in March…

During an episode of the DOJ podcast, Justice Today, Frances Scott, a researcher for the National Institute of Justice (NIJ) Office of Investigative and Forensic Sciences, said the popular model for determining weed impairment by testing THC concentration is flawed in a number of major ways.

Scott said that scientists understand the effects and chemical interactions of alcohol consumption and determining intoxication based on the concentration of alcohol in the blood is “relatively easy.”

But with marijuana, there are too many complicating factors involved to find reliably universal THC markers for intoxication.

Scott points out that there’s a big difference in intoxication levels when someone consumes edibles compared to smoking flower. Smoking produces a high that quickly escalates to a peak and then quickly recedes. Edibles produce a high that gradually builds and gradually recedes over many hours.

Click here to listen to the podcast.

* More from the Shorenstein center on Media, Politics and Public Policy…

Currently, the two most common methods used to measure THC concentration to identify impaired drivers are blood and saliva tests, although there’s ongoing debate about their reliability. […]

Setting a legal limit for marijuana-impaired driving has not been easy. Countries like Canada and some U.S. states have agreed upon a certain level of THC in blood, usually between 1 to 5 nanograms per milliliter. Still, some studies have found those limits to be weak indicators of cannabis-impaired driving.

In the U.S., five states — Ohio, Illinois, Montana, Washington and Nevada — have “per se laws,” which set a specific amount of THC in the driver’s blood as evidence of impaired driving, according to the National Conference of State Legislatures. That limit ranges between 2 and 5 nanograms of THC per milliliter of blood. […]

Saliva tests can detect THC for 8 to 24 hours after use, but the tests are not perfect and can results in false positives, leading some scientists to argue against using them in randomly-selected drivers. […]

In a 2021 report, the U.S. National Institute of Justice, the research and development arm of the Department of Justice, concluded that THC levels in bodily fluids, including blood and saliva “were not reliable indicators of marijuana intoxication.”