Oops! I made a mistake!

Fatigued after an 11-hour flight, Anna grabbed her well-worn suitcase off the luggage carousel. That bag had seen a lot of miles with her. She took a taxi home, left the suitcase near the front door, and collapsed into bed. She’d missed that bed!

Jet lag is rough. She woke up 12 hours later, still feeling bleary. After pouring coffee down her throat, she dragged her suitcase into the bedroom to unpack. But when she tried her usual combination, the lock wouldn’t open. She tried again. Nothing. Swearing, she thought to check the name tag.

Oh no. It  was someone else’s battered black suitcase. Hers was probably still sitting at the airport, but that wasn’t her biggest worry. She’d stolen someone’s stuff! What if the police were already on their way?

Anna can relax. She’s not going to be making a trip to the Big House, at least not over the suitcase.

Mistake can sometimes be used as a defense to criminal charges—but only sometimes, because there are two kinds of mistake.

The first kind is called mistake of fact. It occurs when the defendant was wrong about some material fact, such as Anna believing she’d grabbed her own suitcase. As long as Anna’s mistake was reasonable, it will usually be successful as a defense.

Why? (This paragraph is law geekiness, and you are welcome to skip it if so inclined.) Crimes require that the defendant commit a particular act—or fail to do a particular act, like paying taxes owed. This is called the actus reus, the evil act. But most crimes also require that the defendant have a particular state of mind at the time of the action. This is called the mens rea, the evil mind. Larceny, for example, requires that the defendant take someone else’s property (that’s the actus reus) and that she do so intentionally (the mens rea). So if Anna honestly believes she’s grabbed her own suitcase, she didn’t intentionally take someone else’s stuff and therefore didn’t have the mens rea. So she can’t be convicted.

(Okay, extreme geekiness over.)

The other kind of mistake is mistake of law. This happens when a person believes that the law permits a particular action—but the person is wrong. So if I honestly believe it’s legal to light up a joint in Boise (it’s not), the cops can arrest me and I won’t be able to use mistake as a defense.

The reason behind this rule makes policy sense. If we allowed people to claim mistake of law, well, wouldn’t everyone just purposely avoid learning what the law says?

So here’s a real-life example. Every fall I host a barbecue at my house for my department colleagues. It’s the one (and generally only) time everyone comes to my place. I live in a subdivision with a lot of identical-looking houses. A couple of years ago, one of my colleagues drove to my house, opened the front door (unlocked), and marched inside—only to discover it wasn’t my house. Luckily for her sake, nobody there noticed and she crept back out. But if she had been caught, she’d have had a valid defense.


The case was going badly for the prosecutor. One of her star witnesses had disappeared days before the trial began, another fell apart under cross-examination and retracted most of his original statements, and the primary investigating police officer alienated the jury by appearing arrogant. But just as the prosecutor was ready to give up, screams reverberated from outside the courtroom. A moment later, a bailiff came rushing inside. “Your Honor! Your Honor!” the bailiff shouted. “A spaceship has landed three blocks away and aliens are everywhere!”

Smiling triumphantly and without missing a beat, the prosecutor leapt to her feet. “Your Honor? I move for a mistrial!”

What is a mistrial? Most simply, it’s the cancelation of a trial in progress. Either side can move for a mistrial, and the judge can declare one at any point up until the jury renders a verdict.

Mistrials are rare. They result in huge additional expenditures, plus they represent wasted time for everyone involved. If the defendant has been kept in jail pending her trial, a mistrial means she’s going to spend even more time locked up. For these reasons, the system strongly discourages mistrials. But they do occur.

What could cause a mistrial? Well, rarely is it an alien invasion. But that could be a reason. Anything that makes it impossible for a fair trial to proceed could be cause for a mistrial. Potential causes include:

  • Natural disasters or other serious, long-term emergencies
  • Death of someone critical to the case, such as one of the lawyers or a juror
  • Juror misconduct
  • Serious errors in matters such as choosing the jury or admitting evidence
  • Errors that are fundamentally prejudicial to the defendant, such as the prosecutor making statements she shouldn’t
  • Jurors’ inability to reach a verdict

When I googled for recent mistrials, I found some interesting cases.

  • At a murder trial in Iowa, the prosecutor improperly informed a potential juror that Iowa does not have the death penalty.
  • At a trial in Texas for improperly carrying a weapon, a juror was assaulted (by someone unrelated to the case) outside the courthouse and was too distraught to continue.
  • In a robbery case in Virginia, technical errors meant people in the hallway—including witnesses—could hear testimony going on in the courtroom. Also, one juror kept falling asleep.
  • In a corruption case against the former LA County Sheriff, the jury was deadlocked after four days of deliberations.
  • In a California homicide case, a juror disregarded instructions and looked up the legal definitions of specific crimes.
  • In a Colorado homicide case, the prosecutor withheld evidence of a police officer’s misconduct.
  • In Kansas, a local news station aired footage of potential jurors in a murder case. Interestingly, after the mistrial was declared, a change of venue was also granted.

When a mistrial is granted, the system basically pretends as if the trial never happened. Double jeopardy doesn’t prohibit the defendant from being retried. The prosecutor can choose to drop the case entirely, but most often, a new trial will start from scratch.


Jurisdiction is… interesting. If you watch cop shows or legal dramas, it’s a term you’ve heard thrown around, yet few people have a firm handle on what it means. Today I’m going to fix that.

At its most basic level, jurisdiction simply refers to the legal authority to handle a particular case. Law enforcement agencies have particular jurisdictions, as do courts. Technically, jurisdiction refers to a particular subject matter—that is, whether an agency has power to deal with a particular type of case. A small claims court does not have jurisdiction to hear a murder case. Your local police department does not have jurisdiction to make arrests for federal immigration offenses.

In practice, however, we often use jurisdiction in a geographic sense as well. The LA County Sheriff’s Department has jurisdiction in LA County—and not, say, in Kern County.

Jurisdiction is a complicated issue in the US because our legal system is fragmented. While most countries have a single (federal) court system and a single (federal) law enforcement agency, we don’t. We have state and federal courts, some of them with quite specific areas of authority (such as military cases or bankruptcy cases). And we have many thousands of police agencies at local, state, and federal levels.

Jurisdictions can overlap. Imagine I kidnap someone in Wyoming and drag him to my hometown, only to be caught on the nearby university campus. In that case, dozens of law enforcement agencies might be involved, including the FBI (a federal agency) and many state and local police departments. Just from my own area, my city police, the Highway Patrol, and the campus police might be there (the latter two are both state agencies). It can be confusing! And while agencies very frequently cooperate with one another, sometimes friction or rivalry may exist.

The takeaway for you as an author? If a police department or court is dealing with a case in your book, make sure they have proper jurisdiction. That may require research to determine who handles what, but you definitely don’t want to get it wrong.



High-speed chases

Not long ago, my husband was watching a police chase via live feed on Facebook. The chase covered a long distance, all the way from Inglewood (near central LA) to Kern County, 92 miles to the north. But what’s interesting about this case was the time it took: 2 hours.

Now, I’ve made that drive quite a few times myself—albeit not in a stolen Mercedes—and yes, when traffic is heavy it can certainly take that long. And when you have two little kids in the car with you who decide they need to pee with great frequency? It can take even longer. But you’d think someone eluding the police would manage better than 45 mph, right?

We’ve all seen exciting high-speed chases. I have two fictional movie favorites: Blues Brothers and Raising Arizona. And in real life, high-speed chases do happen. But they’re risky to the officers involved and to innocent bystanders. One study says that since 1979, over 11,000 people have been killed in high-speed chases. Over 5000 of those people were non-violators and 139 were police officers. Years ago, one of my students was doing a police ride-along when other cars got involved in a high-speed pursuit. The fleeing suspect ran over woman and her baby as she pushed a stroller through a crosswalk.

Not only have innocent people died or been injured during high-speed pursuits, but sometimes police departments get slapped with lawsuits by people who were injured or received property damage.

For these reasons, some agencies have banned high-speed pursuits completely. They’ve determined that it’s better to let a bad guy go free than risk everyone else. Most agencies haven’t gone that far, but they usually have policies in place that restrict high-speed pursuits to situations where they consider the suspect a danger to others. They may, however, use helicopters, drones, and other technology to keep tabs on a suspect in a low-speed chase. Or they can just follow him slowly, as happened most famously when OJ Simpson was arrested. In the case my husband was watching, the suspect was apparently wanted initially for trashing a hotel room.

The truth about science and crime

Every crime show ever.

Setting—messy crime scene

Attractive Detective 1: Wow, look at all this blood and semen so helpfully spread all over the crime scene!

Attractive Detective 2: I will collect it and rush it to the crime lab, pronto!

5 minutes later,  setting—gleaming hi-tech crime lab

AD 2, handing evidence to Attractive Lab Tech: This case is super important. We need results pronto!

ALT: Right on it, Detective.

5 minutes later

ALT: Here you go, Detective. Yep, all the DNA definitely belongs to Slimy Suspect. I’m 100% sure.

AD2: Great, thank you!

5 minutes later, setting—courtroom

Stern Judge: I sentence you, Slimy Suspect, to life in prison!

How many times have you watched TV shows with essentially this scenario? There are many inaccuracies here, but today I’m going to focus on one, involving that crime lab.

On TV, the lab gets the evidence and analyzes it, and the suspect promptly finds himself whisked off to jail. In reality, though, evidence analysis takes time. Most of this is due to high demand and limited capacity. It’s estimated that the current backlog may include well over 350,000 cases. And it’s not just DNA from crime scenes, but also drug testing and evidence from rape kits. Depending on the jurisdiction and the case, it may take over a year to get results back from the lab.

Time isn’t the only problem. Labs range in quality and not all are accredited. Their employees also vary in accuracy. There have been numerous reported cases of lab employees making errors in their work, either by accident or on purpose.

And even the best employees of the best labs can’t always get wonderful results. Forensic evidence can degrade or be contaminated. To give a personal example of this, when I was in college and working at a deli, I was robbed at gunpoint. When the police came, they dusted the counter for prints, but we all knew that was a pretty useless activity. Over the course of the day, dozens of people had touched that counter, so distinguishing the robber’s prints from everyone else’s would have been impossible. (They never caught anyone for the crime.)

And even when the evidence is in great shape, an analysis can never deliver absolute certainty. The best it can do is offer a probability of a match. And if the (innocent) suspect has an evil identical twin, he may be out of luck.

Finally it should be noted that DNA and similar evidence isn’t present at most crime scenes. If someone robs a bank, she’s probably not going to leave behind blood or anything else that is an obvious source of DNA evidence.

So those pretty detectives and lab techs might make for fun TV viewing, but they have little to do with law enforcement reality.