LAHAINA, Maui — Maui police will be armed with a new weapon to crack down on Halloween spirits — the liquid kind — when Lahaina town welcomes thousands of revelers to its annual Oct. 31 celebration.

The hand-held Alco-Sensor FST can "sniff" alcohol in cups and other containers and on people who have been drinking. Although the instrument cannot provide a blood-alcohol analysis from these "passive" forms of testing, it can indicate a positive or negative reading for the presence of alcohol — all that's needed in cases of underage drinking or drinking in a historic district, where consuming any amount of booze is illegal.

Lahaina resident Ann Burkhalter said she favors strict enforcement of liquor laws on Halloween night. Burkhalter, husband Bunt and friends are three-time winners of the Maui Tacos Great Halloween Costume Contest.

Every year, she said, people in the Front Street crowd poke, pull and punch at their elaborate costumes or otherwise exhibit hostile behavior, most likely because of alcohol. "The cops don't want to keep people from having fun. They just want to keep them from being obnoxious," Burkhalter said. "Of course, some people are going to be obnoxious anyway."

Maui police acquired 20 of the Alco-Sensor FSTs in February with funding from a U.S. Department of Transportation grant. The Alco-Sensors, manufactured by Intoximeter Inc., cost $490 each. Capt. Charles Hirata, Lahaina District commander, said MPD was the first police department in the state to use the latest version of the Alco-Sensor, but other departments also employ portable breath testers.

The Alco-Sensors are used largely by traffic enforcement officers to catch motorists who are driving under the influence of liquor. A mouthpiece can be attached to allow subjects to blow into the sensor, producing an accurate blood-alcohol content reading. A separate, funnel-like attachment is used to get positive-negative readings from air samples.

Instrument readings cannot be used as evidence, but the results can provide probable cause for officers to take suspected drunken drivers to a police station, where they will be given a formal breath test. Hirata said the devices also can save motorists and police the trouble of hauling in a suspected drunken driver who is not legally impaired.

Hirata said most of the Halloween-night trouble in Lahaina is related to alcohol, and drinking by those under the age of 21 is a foremost concern.

"We have kids coming over here from all over the island. Some are here to have a good time and some can't do it without alcohol," he said. "It gets pretty obnoxious when kids pumped up on alcohol go around wanting to fight everyone."

The LahainaTown Action Committee, the merchants group that organizes the annual Halloween festivities, welcomed the enhanced enforcement.

"We work really closely with the police on Halloween. We want everyone to have a good time, not a passing-out-drunk time," said Jennifer Dory, the group's events coordinator.

More than 60 police personnel will be on duty Monday night, with patrol officers and detectives called in from other districts. DUI checkpoints will be operating, Hirata said.

"We are letting people know ahead of time: Don't come over here and get drunk. Make it a safe night and get home safely," he said.

Hirata issued a separate warning about costumed partiers who carry whips, swords, sharp-edged objects or any real or replica weapons. Police also watch for public indecency, but Hirata said he can't recall any complaints from years past.

With Halloween falling on a Monday, Hirata said he is hopeful that fewer people will turn out. But Dory pointed out that last year's Sunday celebration attracted an estimated 20,000 despite bouts of heavy rain.

Reach Christie Wilson at cwilson@honoluluadvertiser.com.