How often have you heard that blacks use illegal drugs at the same rate as whites but are arrested far more often for using them? This is supposed to prove that the police are hopelessly racist.

The ACLU gets very excited about this. Former Executive Director Ira Glasser said drug laws are “a system of separating out, subjugating, imprisoning, and destroying substantial portions of a population based on skin color.” Sounds bad.

So what are the facts? The US Department of Health and Human Services does regular surveys, and asks people if they take illegal drugs. Blacks are only about 10 to 20 percent more likely than whites to say that they do.

But if you look at the arrest data, blacks are 2-1/2 times more likely to be arrested for drug possession and 3.7 times more likely than whites to be arrested for trafficking. So, is this proof of police discrimination?

If it were, it would be an aberration. In the case of violent crime–rape, robbery, assault–we know that the reason police arrest blacks more often than whites is because blacks are more likely to commit these crimes. We know that because the Justice Department does huge surveys of crime victims and asks them what race the perp was.

About half of all robbery victims, for example, say the robber was black and–sure enough–about half the robbers police arrest are black. The same is true for other violent crimes: Police are more likely to arrest blacks because blacks are more likely to be criminals.

So, do police suddenly go nuts if drugs are involved? If that’s so, there must be a lot of nutty black police officers. Take Washington, DC. Ever since it got home rule in 1975, every mayor in DC has been black. Two thirds of the police officers are black. And yet, the ACLU itself reports that in 2010 a black DC resident was 8 times more likely than a white resident to be arrested for marijuana possession. Was that racist police–racist black police–or just more black dope smokers?

Actually, it’s possible for blacks to be no more likely than whites to use drugs but still get arrested more often for using them, even by scrupulously race-neutral police. That’s because blacks commit so many other crimes. If a black is arrested for robbery–and blacks are about eight times more likely than whites to be arrested for robbery–the police search him for drugs. If they find drugs they charge him with possession in addition to robbery. If he hadn’t got caught for robbery–or assault or murder or whatever it was–he probably would not have gotten that drug charge.

As I said earlier, the idea that blacks don’t use illegal drugs much more often than whites comes from surveys. But when you ask people if they take illegal drugs do they tell the truth?

As it turns out, there is scholarly literature on this. Researchers ask people if they have taken drugs and then take urine or hair samples to find out. And almost every time, blacks are a lot more likely than whites to say they haven’t taken drugs but the test then proves they were lying.

A 2005 study in the Journal of Urban Health, for example, found that blacks were ten times more likely than whites to lie about cocaine. Hispanics were five times more likely. When it came to marijuana, not one of the 109 whites in the sample lied, but one in eight of the 191 blacks lied.

A 2008 study of Vietnam-era veterans in the journal Addictive Behaviors found that blacks were more than 20 times more likely than whites to lie about cocaine, and twice as likely to lie about marijuana.

A 2003 report also in Addictive Behaviors surveyed 290 black men who were being treated for high blood pressure. Only 48 admitted they were using illegal drugs but urine tests found that 131 of them were. Forty-five percent were taking drugs but only 19 percent admitted it.

This behavior goes back a long way. In 1994, more than 20 years ago, a large study of young people, aged nine to 20, found that blacks were six times more likely than whites to claim they didn’t use cocaine–but have it show up in a urine test.

The Journal of Urban Health article I quoted earlier says this, and I quote: “the results replicate and extend a growing body of research suggesting that African Americans underreport substance use on surveys.” Underreport is a nice way of saying that they lie about it.

So, does this prove that there is no bias in drug arrests? Not necessarily. The samples in these studies are limited, and occasionally, the results go the other way.

One 2001 study found that when people arrested for various crimes were asked about drug use and then tested, whites were more likely than blacks to lie about crack cocaine–but less likely to lie about marijuana or methamphetamines.

In general, though, it seems that blacks are a lot more likely than whites to take drugs and then claim they don’t.

But there’s a better way to tell which groups are more likely to use illegal drugs. Every year, the US Department of Health and Human Services tells us how many people went to the emergency room because they took an illegal drug and got sick or went crazy. Since the government tabulates these numbers by race, we can calculate rates. Blacks are 3-1/2 times more likely than whites to go to the emergency room because they took an illegal drug. They are 2.8 times more likely than whites to end up in the ER because of marijuana, and seven times more likely because they took cocaine.

It doesn’t seem likely that blacks just freak out more when they take drugs, but if that’s the case, that would help explain high arrest rates, too: People who are so high they have to go the ER are probably doing things that attract the attention of the police.

Some people might say that white people with drug problems go to fancy private clinics instead of the ER. Doesn’t’ work that way. You go to detox for weeks at a time, by appointment. If you just show up blithering they’ll send you to the ER.

So, the ACLU is wrong. First, it appears that blacks do use illegal drugs more often than whites, but lie about it. And there’s no question they get picked up a lot more for other crimes and if they have drugs on them they’re charged with possession. Finally, they’re 3-1/2 times more likely than whites to end up in the ER because they took illegal drugs.

It looks to me that, as usual, police are just arresting the people who break the law.

So, can we lay to rest this idea of racist police? Apparently not. Just last week, the University of California Student Association–representing the state’s 233,000 college students–voted to urge the university system financially to divest from the United States. I’ll quote you one of the reasons: “racial and ethnic minorities are disproportionately targeted by law enforcement agencies, particularly for drug-related offences.”

The myth lives on. We have a lot of work to do. Thanks for watching.