Gov. Martin O'Malley speaks during a rally outside of the Maryland State House in Annapolis on Jan. 14 in support of raising Maryland's minimum wage. (Jose Luis Magana/AP)

Maryland Gov. Martin O’Malley (D) signed legislation Monday to remove the threat of jail time for possession of small amounts of marijuana but cautioned against legalizing the drug, as Colorado and Washington state have done recently.

Under Maryland’s new law, which will take effect Oct. 1, those caught with less than 10 grams of marijuana will be subject to civil fines, starting with $100 for a first offense, rather than criminal sanctions. Fifteen states and the District have taken similar steps.

O’Malley, a former prosecutor who rose to prominence as a law-and-order mayor of Baltimore, told reporters that he had come to believe that forgoing criminal prosecutions in such cases could allow “a greater focus on the more serious threats to the public health and public safety.”

But he said he also thinks that Maryland should wait to see what happens in other states before contemplating the next step of legalizing marijuana and regulating it like alcohol.

“I don’t believe that this would be a good experiment for us to engage in as a state because there are so many employment options in our state that require the passage of a federal background check and a clean record and sometimes security clearances that all of this could impact,” O’Malley said. “But we will learn from other states, I suppose.”

The governor, who is weighing a 2016 White House bid, said he considers it an “open question” as to whether legalization of marijuana would lead to “more harm or less harm . . . especially when it comes to the development of young minds and young brains.”

His comments followed a ceremony in which he signed close to 150 bills passed during the 90-day legislative session that concluded last week. It was the final session for O’Malley, who is term-limited and steps down in January.

Other measures that got his signature Monday included a second marijuana bill, which makes the drug more readily available to those who seek it for medical reasons. A law O’Malley signed last year limits distribution to academic centers, which have declined to participate.

He also signed several bills Monday meant to curb domestic violence, as well as “Jake’s Law,” which will stiffen penalties for drivers who cause serious crashes while talking or texting on a handheld cellphone. The legislation was filed in memory of Jake Owen, a 5-year-old killed in a 2011 crash.

O’Malley did not voice his support for the marijuana decriminalization bill until the final day of the session.

Supporters of the bill — who included all three Democrats seeking to succeed O’Malley — pointed to racial disparities in the arrest rates for marijuana possession between whites and blacks. And they said the stigma of a criminal conviction can haunt people for years as they look for jobs.

In recent days, local prosecutors have urged him to veto the bill, arguing that it was hastily passed without regard to all of the consequences. The legislation, for example, does not include any criminal sanctions for smoking marijuana in public, including on school grounds. And while possession of small amounts of marijuana will be a civil offense, possession of paraphernalia, including paper to wrap joints, will still be a criminal offense.

O’Malley said he found it compelling that most people arrested for small amounts of marijuana are not sent to jail under current practice.

According to legislative analysts, in 2013, there were 19,828 violations involving the use of less than 10 grams of marijuana in district courts across Maryland, of which 3,099 resulted in fines or incarceration.

“Very few people, if any, ever get time for smoking marijuana,” O’Malley said.

Del. Nathaniel T. Oaks (D-Baltimore), who has advocated for decriminalization of marijuana for more than a decade, said he was glad to see the governor come on board and attributed his position in part to his presidential aspirations.

“I think the times have changed, and the public is saying, ‘This is what we want,’ ” Oaks said.

Del. Heather R. Mizeur (Montgomery), one of the Democrats seeking to succeed O’Malley, said she is hopeful that lawmakers will build on the decriminalization bill when they return next year under a new governor.

“Our work starts now for a more ambitious agenda in 2015: moving the market into the light of day through legalization, regulation and taxation,” she said.

Her opponents, Lt. Gov. Anthony G. Brown (D) and Attorney General Douglas F. Gansler (D), have not pushed for legalization, though Gansler has suggested that it could become law in the future.

Among the other legislation signed Monday were three bills targeting domestic violence that O’Malley had asked lawmakers to pass.

Under one bill, someone who commits a crime of violence in the presence of a child at least 2 years old is subject to an additional five years in prison. The legislation was a priority of Gansler and Brown this session.

Another bill ends Maryland’s distinction as the only state that requires “clear and convincing evidence” to receive a civil protective order. The legislation says that only “a preponderance of the evidence,” a lower standard, is needed to receive such an order.

The third bill adds second-degree assault to the list of crimes for which a person can obtain a permanent final protective order.