But it is individuals whose lives are wrecked by these laws. When Garrett Daley was 14, his 9-year-old adopted sister, Devon, said he molested her. Their mom called the police.

It turned out Devon had lied. It was she who initiated sex with Garrett. She later told the police, but they didn't believe her. Today, seven years later, prosecutors still won't let her change her testimony.

To avoid a jail sentence, Garrett plea-bargained to "attempted molestation of a child." What choice do these kids have? "They're told they'll go to jail for 90 years or 50 years or something, unless they accept this plea, and the plea almost always requires lifetime sex-offender registry," Sen. Johnson says.

Garrett didn't realize his plea bargain would put him in a different kind of jail. Once you're on the sex offender registry or on probation, your life is wrecked, public defender Phillis told "20/20."

"They can't go anywhere children frequent. So that's McDonald's, that's Jack in the Box ... Children have actually been told if you go to a movie and another child walks in, even if it's a rated R movie, then you're to get up and leave."

I told Weiers about the public defender's comments. "The public defenders say all laws go too far," Weirs replied.

Give me a break. State sex-offender registries could separate consensual teen sex from pedophiles who prey on 5-year-olds. Minnesota does that.

Too often, American criminal law is a blunt instrument designed to make it look as if politicians are protecting us. I think the politicians usually protect themselves, at our expense.