LOUISVILLE, Ky. (WDRB) -- A drunk driver who killed two people and never served a day in prison could walk free again on drug and gun charges after police mishandled evidence. 

Rebecca Johnson inked a plea deal in Jefferson County Circuit Court on Tuesday for drug trafficking charges. She admitted to having meth and pills intended for sale, marijuana and drug paraphernalia possession and an amended down charge of possession of a firearm by a convicted felon instead of possession of a hand gun.

"It would have been a tough case to try," said Kirk Rose, Jefferson County Assistant Commonwealth's Attorney. "The firearm in this case was missing ... LMPD's property room had sold it at auction. It got labeled wrong. So therefore, we could not move forward on the most serious charge of this case."

With the plea agreement, Johnson now faces three years in prison or five years of probation. 

"I'm frustrated. I'm very angry and I'm tired of this, " said Tammy Williams, whose son, Justin Cantrell died alongside Ben McIntosh in a DUI crash with Johnson behind the wheel in 2006. "(Johnson) keeps getting off scott free, and I keep telling everyone she's going to hurt somebody else."

Johnson cut a plea deal in 2006 too, and the 20 years she faced in prison for manslaughter ended being just probation. 

The years since Cantrell's and McIntosh's death have been rocky for Johnson. In 2012, she was ordered to serve 45 days in jail after violating the manslaughter probation for a synthetic marijuana conviction in Carroll County.

In 2015, she was arrested again in Oldham County and charged with drug trafficking. That cases ended last week with five more years of probation. 

"All these charges ... how do these judges think probation is going to work with someone like her?" Williams asked. "She's had so, so many chances to turn her life around." 

Johnson's defense has always been a brain injury suffered in the 2006 crash that now impacts her decision making. Tuesday's plea deal in Louisville makes her fourth felony conviction in Kentucky. The fact that none of these cases ended in prison time leaves Williams suspicious of the justice system. 

"Something is not right," she said. "Something is just not right, and with evidence coming up missing, it makes me wonder even more."

Friends of Cantrell and McIntosh launched an online petition trying to put public pressure on the court system to lock up Johnson.

A judge will ultimately decide whether her latest plea deal ends in prison or probation. Sentencing is set for June 8, and Williams plans to attend. 

"I can't bring Justin back to me, but I can work at saving someone else's life and that is my goal," Williams said.

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