What should Illinois set as legal marijuana limit before it's DUI?

  • Joe McMahon

    Joe McMahon

Updated 6/2/2015 8:47 PM

Kane County State's Attorney Joe McMahon said the proposed 15 nanogram THC threshold for DUI-marijuana in a bill awaiting Gov. Rauner's signature is excessive compared to laws in other states, such as Colorado.

One aspect of the bill that has drawn criticism is establishing a legal threshold for a driver to be considered under the influence of marijuana.


Under current law, a driver with any amount of THC in their bodies is automatically considered legally impaired. The state must prove only a person had THC in his system.

Critics have pointed out that THC stays in a person's body for weeks, but the person won't show any signs of impairment.

The new law proposes a threshold of 15 nanograms of THC for a person to be legally impaired to drive.

The Schaumburg-based Alliance Against Intoxicated Motorists says that threshold is dangerous and has urged Rauner to veto the bill.

McMahon also is concerned as some states have thresholds of between 2 and 7 nanograms.

"For Illinois to be a level at two, three or seven times the amount than other states seems inconsistent with highway safety," McMahon said.

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"The goal is for us to have safe roads. I think medical science ought to drive the debate. I don't think it should be driven by the marijuana industry."

State Sen. Mike Noland, an Elgin Democrat, was the chief sponsor of the bill in the Senate.

Noland has said the 15-nanogram threshold was an attempt by lawmakers and the Illinois State's Attorney's Association to strike a balance between the 5-nanogram limit in Colorado and the 25-nanogram limit in Washington, two states where marijuana is legal for recreational use.

"The degree to which we are impaired by alcohol, .08 (BAC) is comparable to 15 nanograms of THC per milliner of blood," said Noland, adding that lawmakers can always lower the threshold going forward.

But Washington's legal threshold for driving under the influence of marijuana is 5 nanograms of THC, according to Brianna Peterson, laboratory manager of the Washington State Patrol's Toxicology Laboratory Division and the Washington State Legislature's official website.


Donald Ramsell, a prominent DUI attorney based out of Wheaton who has been critical of the states's DUI-marijuana laws, declined to say what level he thinks the nanogram threshold should be set.

Ramsell said he is pleased the law will set a standard and prevent people from going to prison if they were not impaired in a crash.

However, Ramsell said he is concerned about the constitutionality of allowing police to conduct roadside saliva tests to determine if a driver is over the 15-nanogram limit.

The bill was sent to Gov. Rauner last month and he has 60 days to sign or veto it.

Rauner press secretary Catherine Kelly declined to specify Rauner's stance on the bill or a time frame as to when he would act.

"The governor will carefully consider any legislation that crosses his desk," Kelly wrote in an email.

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