In a DUI / DWI drunk driving case against an off-duty Chicago cop accused of pointing a gun at a motorist in a road-rage incident, there's a battle.

Officer Kevin Carey was arrested in May and charged with aggravated assault and DUI - driving under the influence, misdemeanors.

Carey, 28, refused to take a Breathalyzer in the criminal case, but took one for the department's internal investigation. He was stripped of his police powers and faces firing.

Now prosecutors are fighting to use the Breathalyzer as evidence in the DUI case. Carey's blood-alcohol level was .145, nearly twice the .08 legal limit, records show.

Prosecutors argued the Fourth Amendment's search-and-seizure protections don't bar them from using the Breathalyzer results. There was probable cause to arrest Carey, so his consent isn't needed, prosecutors say.

The Fraternal Order of Police is defending Carey, arguing in court papers that he was "deceived into agreeing to submit to the tests believing the tests would not be used in his criminal prosecution."

On Nov. 15, Traffic Court Judge Steve Goebel ruled in Carey's favor, throwing out the Breathalyzer results as evidence. But the fight is not over.

"We're planning an appeal," said John Gorman, a spokesman for the state's attorney's office.

Early on May 5, Willie Flood, a coffee server at a hotel near O'Hare Airport, was heading to work on Western near 72nd. He told police he cut off Carey, who then started tailgating Flood's Mercedes SUV.

Flood said he sped north, trying to lose Carey, who allegedly pointed a gun at Flood on the Kennedy Expy. near Division. Flood had called 911 and was on the phone with the State Police when he pleaded, "Before he starts shooting, somebody help me!" records show.

The State Police urged Flood to go to a Northwest Side police station, but he stopped miles away near the 2600 block of North Kedzie when he spotted officers. Flood jumped out and yelled, "There's a man chasing me and he's got a gun!" police reports say.

The officers said they saw Carey pointing a handgun at Flood.

Carey obeyed a sergeant's command to drop his weapon and identified himself as an officer. Carey smelled of alcohol, his speech was slurred and his eyes were bloodshot, the officers said in police reports.

Both men were taken to the Humboldt Park District police station, where Carey was arrested. Flood declined comment. Carey's DUI defense lawyer has not yet given a statement.