EVERETT — Sure, marijuana is legal now, for the most part.

However, enough criminal cases still involve the drug that the Washington State Patrol has increased the number of scientists with special training needed to analyze its chemical compounds, from one to seven. None of them work at the lab in Snohomish County.

Before legalization, any Snohomish County police department could do a quick field test to scientifically confirm that seized plant materials were, in fact, marijuana. That step is required for prosecution. That so-called “leaf test” was standard since the 1970s, said George Johnston, a manager for the state crime laboratory.

The new marijuana laws require that any sample submitted as evidence in a criminal case go through laboratory testing to determine the level of tetrahydrocannabinol, or THC. That applies to every marijuana prosecution for adults, including cases of large grows and trafficking. The state crime lab didn’t add staff, but trained existing personnel on THC-level testing. Juvenile cases only require proof of THC, not the exact level.

The Snohomish County Prosecutor’s Office says that adult marijuana cases have been a low priority for years. Exceptions include driving under the influence and certain felony offenses when there is believed to be a danger to the public, such as someone selling pot to kids.

The THC testing of marijuana leaves is separate from the blood toxicology tests needed for DUI cases. The number of blood samples tested also has increased, though, officials said.

Three of the State Patrol’s labs, in Seattle, Spokane and Vancouver, are equipped with the instrument needed for THC-level testing. Each instrument cost more than $100,000.

“The way Washington wrote the law, it has forced us to change how we do the testing for marijuana,” said David Northrop, a materials analysis supervisor at the Marysville lab. “It’s caused a lot of headaches to be honest.”

Before legalization, a marijuana leaf test could be turned around in less than a day. Now a rushed case, say, one going to trial, might get a two-week turnaround in the lab, and other samples could take 30 days, said Gene Lawrence, the Marysville lab manager.

The Marysville lab sees up to 1,800 samples of illegal drugs a year, and marijuana has become a much smaller portion of that in recent years, Lawrence said.

Since legalization, more than 2,100 marijuana samples have been submitted for THC testing statewide, but the majority of seized drug samples these days are heroin and methamphetamine.

“We’re seeing far fewer marijuana cases at this point,” Lawrence said. Regardless of the changes in scientific testing, the State Patrol continues to warn the public of the dangers of driving under the influence of marijuana. Most DUIs involving marijuana, statewide and in Snohomish County, also included alcohol as a factor.

“They add together to increase the impairment,” said Lt. Rob Sharpe, who oversees the impaired driving section.

“They’re definitely both bad when it comes to driving.”

Rikki King: 425-339-3449; rking@heraldnet.com.