DNA evidence lasts a long time, which is bad news for those who committed crimes years ago, even when they were kids.

A 20-year-old Janesville man was charged in Rock County Court this week because of a cigarette butt found at the scene of a theft in 2015.

The State Crime Lab, which periodically checks DNA from old cases against its DNA databank, got a hit on the cigarette butt March 11, according to the criminal complaint.

The lab tests show the DNA was from Peter J.W. Allen of 620 Lincoln St., No. 4, according to the complaint.

The butt was found in the driveway where a firearm was taken from a car in July 2015 in the 800 block of Thomas Street in Janesville, according to the criminal complaint.

When a police detective talked to Allen on March 15, Allen said he and his friends would “car shop” when they were young and made other statements implying he knew about the gun theft, according to the complaint.

Allen was 16 at the time the crime was committed. State law does not allow adults accused of crimes while juveniles to be charged as juveniles. That’s because the juvenile justice system is not equipped to handle adults.

Allen was required to submit a DNA sample when he was convicted of two misdemeanors, possession of cocaine and marijuana, last year in Marquette County, online court records indicate.

Four years ago, the state expanded the kinds of convictions for which DNA samples must be collected. Now, samples are required for all misdemeanor convictions. Previously, DNA was collected only for felonies and select misdemeanors.

Allen is scheduled to make his initial court appearance Monday, June 3.