Prosecutors have dropped charges against a Rohnert Park man who tried to sell pot on Craigslist, bringing an end to a case that left two juries deadlocked and illustrated the ambiguity of California's medical marijuana law.

Krish Singh, 44, was picked up in an April 2012 police sting after posting an online ad offering high-grade medical marijuana for $2,700 a pound. Undercover Santa Rosa police officers responded to the ad and arrested Singh in the parking lot of the Target store on Santa Rosa Avenue.

Last week, prosecutors dropped felony marijuana possession and sales charges, the District Attorney's office said Monday. Earlier this month, a jury acquitted Singh of having a shotgun shell at the time of his arrest.

Prosecutors twice tried the case before dropping the charges. Both times the jury could not reach a unanimous verdict.

"In essence, left with the result of two hung juries, we decided that we didn't have further resources to devote to the case," said Christine Cook, the assistant district attorney. "We're not sure that another attempt would have yielded a different result based on ambiguities in the law."

Singh said he wept after hearing the charges were dropped.

"When I found out I was cleared, I broke down in tears," said Singh, a UPS truck loader and father of a 12-year-old daughter. "It was a traumatic experience."

Singh, who has a card allowing him to buy marijuana under California's Compassionate Use Act, said his online ad was targeted at other medical marijuana patients with the intent of starting a co-op among legal pot users.

"The law allows people to associate collectively or cooperatively to cultivate marijuana," said Rachel Elliott, the public defender who represented Singh. "There's a lot of ambiguity in the law. Until we have some more specific guidelines, it will be hard to prosecute these cases."

Singh and a partner had a marijuana growing operation in a residence west of Santa Rosa, but they abandoned the enterprise after the arrest, he said.

"Even though I have a card, some law enforcement doesn't believe in my interpretation of the law," Singh said. "All I admitted to was reaching out to other patients. I should have worded my ad differently."

About two-dozen ads posted in the past week on Craigslist's North Bay section advertise marijuana for sale with disclaimers such as: "This notice is intended for California medical cannabis patients in accordance with Prop. 215 and SB 420. This information is not intended for any other purpose illegal, or otherwise."

Singh uses marijuana for his rheumatoid arthritis and ulcerative colitis, he said.

Singh faced a maximum sentence of three years in prison. Prosecutors offered him a plea deal of 90 days house arrest, but he turned it down and chose to fight the charges, he said.

Since his arrest, Singh said a judge reduced his visitation time with his daughter, with whom he shares custody with his ex-wife, to three hours per week.

"Parents of children who attend school with my 12-year-old were stopping their kids from being around her," he said. "The fallout has been pretty bad and I can't possibly capture in words what it feels like."