A handful of Calgary police officers now have drug recognition training. (CBC)

Six Calgary police officers have been certified as drug-recognition experts, so drivers going through roadside checkstops may now be asked for more than a breath sample.

The officers are trained to determine if someone is high on drugs and can ask for body fluid samples to confirm a driver is under the influence, said a Calgary police spokesperson on Monday.

As of July, it is illegal for a driver to refuse the tests.

Drug-impaired driving was already a Criminal Code offence, but the new legislation compels those drivers to take a roadside test, such as walking a straight line.

They can also be taken to a police station for more intensive tests. If they fail those, they could be ordered to give blood, urine or saliva. Refusing those tests would be a criminal offence, as is the case for refusing a breathalyzer.

Other jurisdictions across the country already have drug recognition experts.

RCMP officers with similar training have been partnering with Calgary police at checkstops on the Calgary city limits.

An officer has to go through several steps to get a suspect charged, said Sgt. Patrick Webb.

"To get that person properly charged they have to bring them into the presence of a drug recognition expert, who can look at the person, do certain tests, do certain examinations and at that point they'll be able to determine if an impairment is from a drug."

Richard Muenz, a criminal defence lawyer in Calgary who specializes in driving under the influence charges, said since the law is so new, some people might try to challenge it through Canada's Charter of Rights and Freedoms.

"There would probably be some concerns about whether or not the police have grounds, if they are asking for a blood or urine sample. Because clearly, they are asking then an accused to participate in the case that they are putting together against them. In those particular type of cases there are likely to be some challenges under the charter."