Updated 1:57 p.m. New Haven Police Chief James Lewis will leave his post after his contract expires Jan. 31, he said in a press conference this morning.

Mayor John DeStefano Jr. said at the press conference that the search for a new chief will take two to four months and will be open to outside and internal candidates. Lewis said he will continue to serve as head of the department until DeStefano finds his replacement.

Lewis said that two assistant chiefs, Roy Brown and Kenneth Gillespie, who came to New Haven with Lewis in July of 2008, will also be leaving. The city will be looking for replacements for those two positions as well.

Flanked by DeStefano and other police officials, Lewis said his departure would allow the city to bring stability to the police force by offering the new chief a full four-year term. Lewis had an only 18-month contract because he was technically completing the term of the previous chief.

The last chief, Francisco Ortiz, resigned to work as head of West Campus security for Yale. The resignation occurred on the heels of a corruption scandal within the New Haven Police Department and the publication of a report filled with recommendations on how to fix the department. Ortiz said at the time that he wanted to let a new chief implement the report’s proposed reforms.

Lewis said he has received many requests from community members to stay in New Haven, but his family wanted him to leave.

“Frankly [the requests] made me feel good,” an emotional Lewis said. “But I got an e-mail from my daughter. And she said: ‘The wrong people are voting. I vote: it’s time for you to come home.’ And it is.”

Lewis served as a police chief in Green Bay, Wisc., among other places before coming to New Haven, and he will return home to Wisconsin after he leaves.

Until then, he said, he will help to select his successor.

Lewis’s departure comes as no surprise, Board of Aldermen President Carl Goldfield said. Indeed, at an aldermanic public safety committee meeting last month, Lewis told Ward 22 Alderman Greg Morehead that he was considering leaving the city, Morehead said.

Today’s announcement comes two days after Lewis said in a press conference at police headquarters that the city is on track to have 1,000 fewer crime victims compared to last year. During the first nine months of 2009, he said, crime has declined roughly 12 percent, and it is down in every major category including murder, robbery and assault and excluding rape, which is up 12 percent since last year.

In interviews with the News over the last month, Lewis attributed the drop in crime to his “targeted activity policing” strategy, which seeks to eliminate sources of major crimes in high-risk neighborhoods.

At the press conference Monday, Lewis said two of the department’s tactics to disrupt criminal activity in targeted neighborhoods have been traffic and narcotic enforcement. Lewis said the police have increased traffic citations by 83 percent and in the process increased seizures of drugs and weapons. And just two years after being shut down for a corruption scandal, the reconstituted NHPD’s narcotics unit has made 283 arrests and started 507 investigations.

“We’re trying to create an environment in the city that’s safe and civil,” Lewis said. “We have made great progress, but the [crime] numbers are still too high in every category.”

Lewis attributed much of the city’s crime to two troubled populations in the city: students who fail or drop out of the school system and ex-convicts.

Police use drug money they have seized from investigations to increase after-school activities, and city officials have created the Prison Reentry Initiative to provide programs such as job training to integrate ex-felons into the community.

Several aldermen said in recent interviews that they had mixed views of Lewis’ policing techniques. Morehead — who is vice chair of the aldermanic public safety committee and whose district includes Silliman, Timothy Dwight, Ezra Stiles and Morse colleges — praised Lewis’ policies, adding that he had hoped Lewis would stay in New Haven because the chief “has turned the police department around in a positive way.” But Ward 10 Alderman Allan Brison said Lewis and his tactics “have ushered in a new mistrust of the police among New Haven youth, which did not exist 10 years ago.”

Brison added that he hoped the NHPD would implement more community-friendly tactics, such as beat patrols, which Lewis eliminated near the beginning of his tenure because he said they were ineffective in reducing crime.

Lewis said he hopes that his tactics will continue no matter who is chief.

“I would hope staff here feel the strategies are showing results and continue them,” he said at the press conference.

Goldfield added that Lewis’ replacement will also be able to decrease crime.

“Nobody’s irreplaceable,” he said.

At Monday’s conference, Mayor John DeStefano Jr. said he will not cut staffing for the NHPD despite an expected budget crunch.