DENVER — Police in some medical marijuana states who once routinely seized illegal marijuana plants by ripping them out by their roots and stashing them away in musty evidence rooms to die are now thinking twice about the practice.
From Colorado and Washington state to California and Hawaii, police are being sued by people who want their marijuana back after prosecutors chose not to charge them or they were acquitted.
In some cases, the one-time suspects are asking for hundreds of thousands of dollars to replace dead plants.
Concerns over liability have prompted some agencies to forgo rounding up the plants or to improvise by collecting a few samples and photographing the rest to use as evidence for criminal charges.
‘‘None of us really are sure what we’re supposed to do, and so you err on the side of caution,’’ said Mitch Barker, executive director of the Washington Association of Sheriffs and Police Chiefs.
The change comes as the notion of marijuana as medicine clashes with police seizure procedure that was developed in an era when marijuana was a scourge that needed to be wiped out.
‘‘Law enforcement is going to have to think more carefully about what their procedures are and how those procedures might need to change in light of changes in the law,’’ said Sam Kamin, a University of Denver law professor.
Just as the smell of marijuana smoke may no longer be grounds to search a home or make an arrest, Kamin, who helped craft the state’s marijuana regulations, said, ‘‘The same evidence that two or three years ago would have given police probable cause today doesn’t.’’
Most local police say they are seizing less marijuana post-legalization, but they still investigate if they suspect patients are growing more than they should. Federal agents face no such quandary since marijuana remains illegal under federal law.
Whether state laws require, as they do in Colorado, police to return medical marijuana intact if a suspect is not charged or is acquitted, departments have been sued over marijuana that has wilted in their evidence lockers.
In Colorado Springs, a cancer patient who had faced drug charges is suing police after 55 dead plants, worth an estimated $300,000, were returned to him. The state appeals court had to order the police to return them.
Medical dispensary owner Alvida Hillery sued police to return her 604 marijuana plants or pay $3.3 million after she was acquitted of drug cultivation charges. She dropped the suit in exchange for a city dispensary license. By then, the plants had died.
‘‘We need uniform rules, and law enforcement would be wise to develop those rules otherwise they will continue to be sued,’’ said Hillery’s lawyer, Sean McAllister, who is representing another dispensary owner in a similar suit in federal court.
City patrol officers must now call a narcotics detective for advice if they believe they are in the presence of illegal marijuana.
In Oregon, a narcotics task force takes only the numbers of plants necessary to bring a patient back into compliance with the law, Washington County Sheriff’s Sergeant Chris
‘‘Ten years ago, you had that many plants, you just went in there and ripped them all out. Now, you’ve got to ask a few questions,’’ said Sergeant David Oswalt, who supervises the Grand Junction police evidence room.
Oswalt’s department tells officers who believe the questionable marijuana is legal for medical purposes to take clippings and leave the plants behind. If not, they can seize plants by the bundle.
Leaving plants behind carries obvious risks, Jim Gerhardt of the Colorado Drug Investigators Association said.
‘‘It would be like arresting a cocaine dealer and taking a minuscule amount of the cocaine as a sample and then leaving it there for them to be used or sold,’’ he said. ‘‘It’s a complicated, messy issue.’’
Washington state does not require police to return plants to acquitted patients. The state’s medical marijuana law allows gardens of 45 plants or less, though it doesn’t expressly prohibit having multiple gardens on a single property.