Researchers are working on a device that will be able to tell if someone is under the influence of marijuana.
The breathalyser, being developed at Washington State University (WSU), would work in a similar way to the alcohol breath test used by police forces around the world.
One of the reasons the research is being led in the US state is because since it became legal for licensed shops to sell the drug earlier this year, "stoned" drivers have become a more regular occurrence.
There is no current form of breathalyser for marijuana use and police officers must use blood tests to determine levels of THC - the active chemical in the drug.
Herbert Hill, lead researcher at WSU, says that while the test will not initially be able to tell the exact level of THC in the blood it will be able to tell if there is any present or not. This should allow the police officer to know whether they can make an arrest or not.