Lindsay Brown had every reason to be excited. An honor student and National Merit Scholar just weeks away from graduating from Estero High School in Estero, Fla., she had earned an academic scholarship to Florida Gulf Coast University.

Moreover, she'd gotten her own apartment and moved in over the past weekend. Everything was going her way until that Monday afternoon, when a security officer asked Lindsay to accompany him to the school parking lot.

The officer pointed out a kitchen knife lying on the floor of Lindsay's car. She was surprised to see the knife and realized it must have fallen out of one of her moving boxes. No matter. She was promptly arrested, handcuffed and hauled off to the Lee County jail. School officials suspended her and banned her from graduation events.

Thus Brown became another overly punished victim of the movement toward "zero-tolerance" policies in schools.

No one argues that students should bring knives to school. But there's a big difference between a kitchen knife inadvertently left on the floor of a car and a switchblade concealed for use in an after-school brawl. "Zero-tolerance" policies permit no such distinction.

Lindsay was charged with felony weapons possession. After nine hours in jail -- among real criminals -- Lindsay's parents bailed her out. A week later, prosecutor Joe D'Alessandro dropped the charge (one that could have sent her to prison for five years). He said the law required proof beyond a reasonable doubt that Lindsay knew the knife was in the car.

Her principal, Fred Bode, said the punishment was justified. Added Lee County Sheriff Bill Byrus: "This young lady made a bad choice." Nonsense. She made no choice at all.

Which is exactly the point.

Criminal law is supposed to be about punishing those who deserve it. To be culpable for a bad act (actus reus) a person also must have criminal intent or a "bad mind" (mens rea). Clearly, Lindsay didn't mean to bring a knife to school.

The principle that both a bad act and bad intent must be present for an act to be considered a crime is well and long enshrined in our law. Bad acts without bad intent (i.e., accidents) can be addressed through the civil justice system.

For example, in 1948, Joe Morissette, a Michigan resident and World War II veteran, collected $84 worth of rusty scrap metal that, unbeknownst to him, belonged to the federal government. He was arrested, charged and convicted of stealing government property after the trial judge told the jury to ignore the innocent intent. The Supreme Court threw out the conviction but said the government was free to sue him for $84 in civil court.

Justice Robert Jackson wrote: "The contention that an injury can amount to a crime only when inflicted by intention is no provincial or transient notion. It is as universal and persistent in mature systems of law as belief in freedom of the human will and a consequent ability and duty of the normal individual to choose between good and evil."

"Zero-tolerance" policies ignore the distinction between wrongful and innocent intent. Instead, they focus on the act alone: You bring a knife to school, you go to jail. This may be more efficient and less subject to arbitrary enforcement, but it invites only contempt for the criminal justice system.

Lindsay Brown is far from the only student to learn that "zero-tolerance" means zero reasonableness. Troubling cases abound:

• A high-school student in Prince William County, Va., arrested on four felony charges for conducting a common chemistry trick, off-campus, that makes a plastic soda bottle burst; 
• A sixth-grader in Tallahassee, Fla., with a manicure kit charged with possession of a weapon on school grounds;
• A high-school junior in Ascension Parish, La., arrested on two felonies after a sketch of military planes attacking a school inspired a search of the student's car that turned up a utility knife used for the student's part-time job.

None of these kids had criminal intent. All went to jail.

Justice is about reason. It's about examining every case in its own right. It is not uncaring and indiscriminate. Doing the right thing -- living right -- should account for something.

We should have zero tolerance, all right -- for the mindless policies that led to these abuses and policy-makers who seek to criminalize everyday accidents and oversights.

Paul Rosenzweig is senior legal research fellow in the Center for Legal and Judicial Studies at The Heritage Foundation (heritage.org) and adjunct professor of law at George Mason University. Trent England is a legal policy analyst in the Center. Read more about these issues at www.overcriminalized.com .