Colorado Supreme Court Rejects State’s Use of “Preliminary” Breath Test for “Impeachment” Purposes

When investigating a driver for a suspected DUI, police routinely ask the suspect to consent to a “preliminary” breath test, conducted by means of a portable device. Suspects are often told that the results are merely to assist the officer in the investigation and that they are not admissible in court. This “preliminary” breath test (PBT) is not the same thing as the more elaborate and reliable breath test, typically conducted with the Intoxilyzer 9000, after the officer has decided there is probable cause to arrest the suspect and invoked the Express Consent Law. Voluntary participation in the “preliminary” test is completely optional and, unlike the situation where the Express Consent Law has been invoked, there are no consequences for refusing to consent to a PBT.  It is rarely a good idea to consent to a PBT or any other voluntary roadside test. Nonetheless, the majority of DUI suspects consent to PBTs, erroneously thinking that it will give them “two bites at the apple,” or because they don’t understand that it’s optional, or simply because they find it hard to decline any request from an authority figure, such as a police officer.

C.R.S. section 42-4-1301(6)(i)(III) provides that the results of a preliminary breath test may not be used as evidence of guilt at trial, presumably because the device has such limited accuracy. However, until this week, no Colorado appellate case had yet decided whether positive results could be used for limited “impeachment” purposes, to contradict a defendant who testified that he had ingested no alcohol at all.

In Cain v. People, 2014 CO 49 (decided June 16, 2014), the Colorado Supreme Court unanimously decided this week that the plain language of the statute means that PBTs may not be used in the trial on the merits, whether as substantive evidence or as impeaching evidence. In doing so, it reversed the ruling of a trial court to the contrary as well as the conviction of the defendant, who was forced to sacrifice his right to testify in view of the trial court’s ruling.

Drivers should still understand that the results of PBTs, no matter how unreliable, can still be used against them in pretrial hearings involving the determination of probable cause to arrest, which is often the most important issue to be resolved in the case before it ever goes to trial.