SACRAMENTO (CBS13) — It’s been four decades since Shirley Derryberry’s 13-year-old sister Doris was killed in cold blood.

But the cold case is now over, thanks to new DNA evidence linking two cousins to the crime.

“I wanted to climb across the wall and choke ’em but that puts me in the same category they’re in,” said Derryberry.

Derryberry says the killers responsible for her sister’s vicious rape and murder would not be caught today, because of new laws.

Under current state law, cops can collect DNA only from felony suspects. But under Proposition 47, many violent crimes are reduced to misdemeanors, and there are far fewer DNA samples taken.

“Here we are covering for a small percentage of the population,” said Assemblyman Jim Cooper.

Assemblyman Jim Cooper says he has a common sense solution. The former Sacramento County Sheriff’s deputy says his proposed law would allow cops to collect DNA for crimes downgraded to misdemeanors.

“When those cold cases were solved…those homicides, rapes, vicious murders….they were solved not from that case, they got solved because they got DNA from a theft crime, or drug crime,” said Cooper.

Assembly bill 16, DNA collection, is a reintroduction of Assembly bill 390, from Cooper’s first term. The bill failed last year, because critics argue, its unfair. The California Attorneys for Criminal Justice says, not all crimes are equal.

“The government cannot collect your DNA unless there’s good reason. Good justification. If they have evidence absolutely we understand that,” said Ignacio Hernandez, a lobbyist for the California Attorneys for Criminal Justice.

Cooper says stories like this is reason enough. Shirely Derryberry’s sister never made it past middle school. And her parents died wondering who killed their little girl.

“She’ll always be in my heart,” said Derryberry.

Shirley Derryberry will be testifying at the bill’s first committee hearing next Tuesday.