A police officer’s sniffing of a teenage partygoer’s breath for alcohol constituted custodial questioning that triggered the right to Miranda warnings, a state appeals court has held.

Absent those warnings, defendant Zeb Koch’s alleged admission to chugging a beer should have been suppressed, the Appellate Division said in reversing his conviction for underage drinking.

The case, State v. Koch, A-602-10, stemmed from what was described as a raucous party of minors on May 8, 2009, in Independence, attended by Koch, 18, and his girlfriend, Ashley Perch, 19.

Local police responded to the home after a neighbor complained about youths smoking marijuana and urinating on his lawn. Several partygoers fled, but Patrolman Joseph DeWitt told the 40 to 50 people remaining that they were not allowed to leave. He then lined the guests up and sniffed each one’s breath, checking for a scent of alcohol. Koch, as the officer approached him, blurted out “I only had one,” DeWitt testified.

DeWitt let the guests leave and issued no citations. But later that night, he stopped the vehicle that Koch was driving, along with Perch and another passenger. DeWitt spoke briefly with Koch and then told him go, but four days later he issued him a summons for underage drinking in violation of an Independence ordinance.

At trial before Municipal Court Judge J. Edward Palmer, Perch testified that she was with Koch throughout their time at the party, and that Koch did not consume alcohol and did not admit to drinking while detained by DeWitt.

Koch, too, testified that he had consumed no alcohol that evening.

Palmer convicted Koch of violating a local ordinance, and ordered him to pay a $250 fine and $33 in court costs.

Koch appealed, and after an August 2010 trial de novo, Warren County Superior Court Judge John Coyle affirmed Palmer’s ruling.

In an unpublished opinion Monday, Appellate Division Judges Ariel Rodriguez and Christine Miniman reversed the conviction, holding Koch “has raised a valid Miranda issue.”

They pointed out that the partygoers’ detention lasted 20 minutes, during which they were not free to leave.

“DeWitt’s sniffing of their breath was clearly in a custodial setting,” the panel said. “His actions were an implied question to Koch and others to indicate whether they had consumed alcoholic beverages.”

The panel cited the U.S. Supreme Court’s 1980 decision in Rhode Island v. Innis , 446 U.S. 291, noting that custodial interrogation can consist not only of express questioning, but also of other words and actions “that the police should know are reasonably likely to elicit an incriminating response.”

Even if DeWitt’s testimony that he smelled alcohol on Koch’s breath were believable, it would be “insufficient as a matter of law to sustain a conviction,” the court said.

“There were many young people at this party,” the panel said. “Alcohol was being consumed by many of them. Therefore, the smell of alcohol in the area of the party was a given.”

The appeals court also took issue with Judge Palmer’s refusal to admit into evidence the squad-car tape of the stop of Koch’s car. Koch proffered the tape to show that he was driving the car, contrary to DeWitt’s testimony that Perch was driving and that she was 17 years old.

Palmer excluded the tape as irrelevant, but the appeals court said it “tended to raise a reasonable doubt about the credibility and accuracy of DeWitt’s identification of Koch as one of the partygoers who consumed alcohol.”

Independence Township Attorney Judith Kopen, of Gebhardt & Kiefer in Annandale, notes that the township was required to respond to the appeal but directed her to file only a statement, rather than a full brief. She declines comment on the opinion.

Koch’s lawyer, John Scollo of New Community Corp. in Newark, did not return a reporter’s call seeking comment.