OREGON: About 15 years ago, when she was in her 20s, Erika Walton handed a bong to someone who turned out be a police officer, and was cited for marijuana possession. She paid the fine, she said, but the violation lingered on, haunting her record.

On a recent afternoon, Ms. Walton was at a free legal clinic here in Oregon’s largest city, filling out paperwork to have that infraction forever sealed. Once the process is complete, she will be able to legally say to an employer, landlord or anybody else who asks that she has never been convicted or cited for any drug crime at all.

“It’s taken away a lot of my life,” Ms. Walton said as she inked out her fingerprints, which Oregon requires applicants for sealing to file. The mark on her record was minor — a citation for possession under Oregon law, even back then, was below the level of a misdemeanor, roughly equivalent to riding the light rail without a ticket. But it still cost her, she said, when she had to divulge it on applications for jobs and volunteer positions at her children’s school.