When Yale Police Department officers broke up Pierson Colleges’s annual Inferno party on Oct. 27, they issued citations to several underage students in possession of alcohol. But many party-goers were confused about the police presence at the party — some even thought the officers were costumed students playing a prank.

“I was surprised,” Nathan Stevens ‘11, who was at the Inferno when the police arrived, said. “I’ve heard they [YPD] were lenient until lately. It’s surprising to me that they were handing out citations for a party going on in Pierson that was pretty much under control.”

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Yale police officers wear New Haven Police Department badges and are invested with their powers of arrest through the City of New Haven. Although the YPD’s primary jurisdiction is limited to the University and its affiliates, and its officers typically deal with on-campus incidents like the Inferno, the department has citywide jurisdiction.

The NHPD actively patrols the entire city of New Haven. The city is split into ten patrol districts — much of central campus is located within the “Downtown” patrol district.

But some students interviewed said it is difficult to draw the line between the YPD and NHPD.

Kristen Windmuller ’08 said she thought the YPD and the NHPD are simply different branches of the same police department. Michael Libertin ’10 said he thought YPD is a subsidiary of NHPD. In reality, YPD spokesperson Sgt. Steven Woznyk, who served in the NHPD for 17 years until he retired as a sergeant, said the YPD and the NHPD are two separate entities that work very closely.

The original force — which was established in 1894 and consisted of just two officers who were, at the time, still city officials — was launched both because students perceived prejudice from city police officers and as a general effort to quell town-gown tensions.

Even though the YPD is now a separate entity that employes officers privately hired by Yale, the department still preserves its links to the NHPD. Both the YPD and NHPD are obligated to provide services to New Haven residents, Woznyk said, regardless of the jurisdiction under which a particular incident may fall.

Woznyk said the YPD listens to NHPD radio transmissions and vice versa and officers from both police departments attend each others’ staff and crime analysis meetings.

Though the YPD and NHPD’s recruiting drives are distinct from another, every new hire to either force must be approved by the New Haven Board of Police Commissioners, NHPD spokesperson Joe Avery said. Regardless of which department an officer works for, he must fulfill the requirements outlined by the state of Connecticut, Avery said.

“Even though we enjoy full jurisdiction throughout the city of New Haven, there are often times where the NHPD will be the primary force,” Woznyk said. “But there are also times when a YPD patrol will be in close proximity to where a NHPD call is put in, and YPD is able to respond quickly and provide the appropriate services.”

When Branford freshman Andromahi “Mahi” Trivellas was struck by a car on Oct. 14, for example, a YPD squad car was first to respond to the scene. Although Trivellas is a Yale student, the hit-and-run occurred on a city street and was therefore under the NHPD’s jurisdiction. New Haven police have therefore been the lead investigators of the accident.

“We work wonderfully together,” Avery said. “We have very close relationships with officers at the YPD.”

Despite the seeming exclusivity of YPD’s jurisdiction at Yale, YPD also works closely with NHPD to train for campus emergencies. In the aftermath of the shooting at Columbine, YPD and NHPD officers went through “active shooter training” together, Woznyk said.

The YPD is also in the beginning phases, he said, of putting together a Special Emergency Response Team — the equivalent of a SWAT team.