Did Marijuana Kill Michael Brown?

Prosecutors suggested to a grand jury that reefer madness caused the behavior that led to a police shooting.

When a blood test found traces of marijuana but no other psychoactive substance in Michael Brown's body, I thought it would take the wind out of attempts to blame his death on drugs. I was wrong about that, as you can see if you read the transcript of the testimony heard by the grand jury that rejected criminal charges against Darren Wilson, the Ferguson, Missouri, police officer who shot and killed Brown on August 9.

Wilson testified that the unarmed 18-year-old attacked him without provocation, punching him in the face through the window of his police car and trying to grab his gun. He said Brown had "the most intense aggressive face" and looked like "a demon." He also likened Brown to Hulk Hogan, the professional wrestler. After Wilson fired two rounds, one of which grazed Brown's hand, Brown took off, and Wilson got out of his car to follow him.

By Wilson's account, Brown stopped running away at some point for no apparent reason, turned, and charged Wilson. Wilson said Brown continued to charge him even after he was struck by five additional rounds, forcing Wilson to fire the final, fatal round into Brown's head. "It looked like he was almost bulking up to run through the shots, like it was making him mad that I'm shooting at him," Wilson said. "And the face that he had was looking straight through me, like I wasn't even there, I wasn't even anything in his way."

Wilson's description of Brown's behavior—in particular, the murderous rage, the extraordinary strength, and the resistance to bullets—is reminiscent of the effects that have been attributed to various illegal drugs over the years, including PCP, crack cocaine, methamphetamine, and the synthetic stimulants known as "bath salts." But it has been many years since people talked about marijuana this way.

During the 1920s and '30s, anti-pot propaganda portrayed marijuana as a "killer drug" that inspires irrational violence. By the 1960s, however, marijuana had acquired a reputation as a "dropout drug" that renders its users placid and lethargic. It hardly seems plausible that such a drug could cause the behavior described by Wilson. Yet that is what Kathi Alizadeh and Sheila Whirley, the assistant county prosecutors guiding the grand jury as it considered the evidence against Wilson, repeatedly suggested.

Although Wilson reportedly had the impression that Brown was on drugs the day of their deadly encounter, he did not broach the subject during his testimony. That task fell to Alizadeh and Whirley, who wanted the jurors to know that high doses of THC can cause "paranoia," "hallucinations," and "psychotic episodes."

Testifying on November 4, St. Louis County's chief toxicologist, Christopher Long, emphasized that such reactions are rare. "You smoke a joint and you chill out," he said. "That's generally what happens….If you take a massive dose, you can get significantly different effects—those effects that are not generally associated with marijuana."

But according to Long, Brown's blood contained 12 nanograms of active THC per milliliter, which he said would not be unusual for a recreational user who had smoked pot within the previous two hours. To put that number in perspective, a 1992 study reported in the Journal of Analytical Toxicology found that subjects smoking a single joint had concentrations above 100 nanograms per milliliter immediately afterward. THC levels then dropped sharply, dipping below 20 nanograms after about 45 minutes but remaining above 10 after an hour. Daily marijuana users may register higher than that and still function normally.

In other words, it does not look like Brown took an unusually large dose. Alizadeh tried to obscure that point by noting that Brown's THC level was "over twice" five nanograms, the cutoff that Colorado and Washington chose for drugged driving after legalizing marijuana. But that standard is highly problematic, treating many regular users as impaired even when they're not. The fact that Brown exceeded that arbitrary limit does not necessarily mean he was too impaired to drive, let alone that he was impaired enough to charge a cop firing bullets at him.

Alizadeh further confused the issue in this exchange with Long:

Alizadeh: Could you experience the hallucination and/or the psychosis if you had a high enough dose of THC?

Long: If you got a high enough dose, you could have a psychotic episode into hallucinations, yes.

Alizadeh: Now, in this particular case, when you tested the blood and you got 12 nanograms per milliliter for the delta-9-THC, do you consider that a high dose?

Long: OK—

Alizadeh: What conclusions did you make from that?

Long: Well, you have to put things in perspective. This was a very large individual. I think he was about 300 pounds. So for concentration of 12 nanograms in a large person, that shows it was a large dose. In a small person, say like 100 pounds, to get to 12 nanograms wouldn't take a lot. A single joint could easily do that. But when you talk about a larger body mass, just like drinking alcohol, larger persons can drink more alcohol because they have the receptacle to hold it.

By conflating the total amount of THC consumed with blood concentration, this exchange implies that 12 nanograms of THC per milliliter will make a large person crazier than a small person, which makes no sense. If smoking a single joint can raise a 100-pound person's THC concentration that high, and if 100-pound people who smoke a joint do not commonly behave the way Wilson claims Brown did, why should we believe marijuana helps explain why Brown is dead?

Testifying on November 13, the renowned forensic pathologist Michael Baden, who was hired by Brown's family to conduct an independent autopsy, said "the amount of marijuana he has could cause abnormal behavior but usually doesn't," adding that "99 out of 100 people taking marijuana aren't going to get in a fight with a police officer." The latter observation prompted Alizadeh to question Baden's credentials. "Although you have a working understanding of toxicology," she said, "you are not a toxicologist, correct?"

While questioning Long and several other witnesses, Alizadeh and Whirley spent considerable time insinuating that Brown had consumed cannabis in the form of the concentrate known as "wax," even though there does not seem to be any evidence that he did and even though it would not matter if he had. If the issue is Brown's level of intoxication, the amount of material he burned to achieve it is irrelevant. The testimony and speculation about wax looks like an attempt to exoticize a familiar drug that people do not usually associate with demonic rage or Hulk-like strength.

Then again, marijuana may be exotic enough as far as the prosecutors are concerned. "You explained that the Delta-9-THC has a psychoanalytic effect?" Alizadeh said to Long at one point. "Psychoactive," the toxicologist corrected her. Later Whirley asked Long, "Could this amount of THC that was found in the blood be—is it possible that someone [could be] ingesting that amount on a regular basis and not be dead?" The toxicologist explained that "marijuana really isn't lethal." Unless you smoke it before getting stopped by a cop, I guess.

Alizadeh and Whirley clearly don't know much about marijuana, but they seemed determined to leave jurors with the impression that it made Brown unhinged enough to behave in the suicidally irrational manner described by Wilson. Why? Possibly because the grand jurors would have trouble believing Wilson's story, which was contradicted by some eyewitnesses (although supported by others), unless the prosecutors offered some seemingly plausible explanation for the bizarre behavior that Wilson says forced him to kill Brown.

Strictly speaking, it was not the prosecutors' job to make Wilson's self-defense claim seem plausible. Ordinarily they would be trying to persuade the jurors to indict the subject of an investigation. But in this case, St. Louis County Prosecuting Attorney Robert McCulloch went out of his way to avoid prosecuting Wilson without having to make that decision himself. Among other things, that required reviving marijuana myths that were hoary when McCulloch was born.