FOND DU LAC, WI (WTAQ) - Wisconsin police agencies are required to hang onto a lot more evidence than they used to.

A 2005 state law preserves physical evidence in a criminal case until the convict is out of prison and off probation. And then, police need a defense lawyer’s approval to get rid of it.

The idea is to help those wrongfully convicted by making it easier to prove that somebody else committed their crimes.

Fond du Lac Police say evidence rooms around the country are growing exponentially. Detective Lee Mikulec told the Fond du Lac Reporter that a lack of space is a huge issue. His department has 50-thousand items of evidence crammed into three rooms and a caged area.

They have everything from electronics to weapons to refrigerated blood and DNA. Drugs are handled differently.

Dodge County Sheriff Todd Nehls said marijuana is burned after a suspect is sentenced.

Mikulec says guns used in suicides are kept for a year in the event that the case turns into a homicide. Illegal weapons like knives are often melted down when the holding period expires. Guns either go to the State Crime Lab, or are used by agencies for the street or target practice.

Vehicles which are seized can either be auctioned off, or used as trade-ins for the new squad cars.

Proceeds from auctioned evidence often go to the State Common School Fund, which benefits public school libraries.