"Zero tolerance" policies continue to result in injustices to our nation's public school students.

In one of the latest examples, a North Carolina school district's application of zero tolerance may cause 17-year-old senior Ashley Smithwick, described by local media as a standout student-athlete, to miss the rest of her senior year.

Far worse, local prosecutors' apparently wooden enforcement against Ashley of a poorly written and dangerous criminal law may end up tacking a lifelong criminal conviction onto Ashley's résumé, thus hamstringing her ability to attend the college of her choice.

Media reports state that Smithwick is a soccer player with a 3.5 grade point average who takes college-level courses. Her so-called crime? Having a paring knife with a slightly longer than 2-inch blade in a reusable lunch sack that was in her purse.

School officials found the puny knife, which they steadfastly refer to as a "weapon," when searching several students' belongings for marijuana or other drugs.

No drugs were found in Ashley's possession, but local prosecutors nonetheless charged her in December under a North Carolina statute that makes it a Class 1 misdemeanor to possess or carry "any sharp-pointed or -edged instrument ... on educational property."

She faces the possibility of six months to a year in prison for this outrageous criminal charge.

Ashley and her parents say that she had the knife in her bag because she accidentally took her father's lunch bag to school rather than her own identical bag. They say the knife was in with Joe Smithwick's lunch so he could slice an apple.

The law's only exception is for "instructional supplies, unaltered nail files and clips and tools used solely for preparation of food, instruction and maintenance."

In other words, the law also applies to a worker who possesses a screwdriver or utility knife on school grounds as part of a construction project.

When criminal laws are this poorly drafted, the last protection for the innocent is the good sense and discretion of prosecutors deciding not to charge otherwise innocent conduct. That good sense and discretion seem to have gone missing in Ashley Smithwick's case.

Neither school officials nor police have suggested that Ashley ever intended to use the pitiful paring knife as a weapon.

As is often true of school officials who hide behind "zero tolerance" policies, Lee County school officials seem unmoved by this fact. School Board Chairman Shawn Walters explains the school district's position as follows: "There is a policy ... that is a standard policy for us that we follow. It is pretty much zero tolerance."

Lee County is by no means alone in its use of "zero tolerance" discipline policies. Consider Estero High in Fort Myers, Fla. There, Lindsay Brown, a senior honor student and National Merit Scholar, wound up charged with a felony because she parked her car at school and a dinner knife — not a sharp knife but the sort you use to spread butter on bread — was on the floor of the car.

Just like the school board chairman in the Smithwick case, Lindsay Brown's principal declined to make an exception for Lindsay's kitchen implement. "A weapon is a weapon is a weapon," he told the local paper.

In Ashley Smithwick's case, Lee County Commissioner Jim Womack wanted to bring in a third party to negotiate between the school district and her family to achieve a more appropriate resolution. So far, Womack appears to be the sole voice of reason and common sense among Lee County officials.

"You hate to see anything like this happen to any teenager," Womack said, "especially one that doesn't have a track record of this behavior." Adds Womack: "The Smithwicks seem to be victimized ... because their daughter unconsciously made a mistake."

That is exactly the point. Students should not be punished as criminals for making honest mistakes. Criminal punishment should be reserved for those who knowingly and voluntarily engage in conduct that they know is unlawful or otherwise wrongful. Criminal charges and punishment shouldn't be directed against otherwise law-abiding Americans who violate a law only accidentally.

As others have pointed out, doing otherwise undermines respect for the law. Similarly, the mindless application of "zero tolerance" policies severely undermines students' respect for the school's authority — and results in unfairness and injustices to individual students.

Public school officials are often between a rock and a hard place in our ultralitigious society, and their lives and decisions are made easier by being able to apply a "zero tolerance" policy against even good students such as Ashley Smithwick. But these policies make a mockery of school discipline and wreck young peoples' lives.

Walsh is a senior legal research fellow at The Heritage Foundation.