A Pennsylvania legislator introduced a bill Monday that would give medical marijuana patients a chance of expunging a conviction of marijuana possession if the charge resulted from their use of cannabis for medical purposes.

The bill is sponsored by State Sen. Daylin Leach (D-Montgomery), and does not have any support yet from Republicans who control the legislature. To be expunged, patients would have to prove they had a doctor's diagnosis for one of the 21 approved serious health conditions at the time of the conviction. The patient would also have to provide evidence they were using cannabis to treat the condition.

Qualifying ailments in Pennsylvania include ALS, cancer, Crohn's disease, glaucoma, Inflammatory Bowel Disease and Posttraumatic stress disorder (PTSD).

"People who have used marijuana for medical purposes do not deserve to have a criminal record. I've met countless Pennsylvanians who have told me that marijuana is the only medicine that relieves their pain," Leach said in a statement. "This will give people the opportunity to go to court and prove that they do not deserve to have a criminal record."

Police in Pennsylvania arrested about 19,700 people for marijuana possession in 2016, according to the FBI's Uniform Crime Report.