By Chris Francescani

(Reuters) - A New York civil liberties leader called Thursday for the police department to sharpen the language it uses to train officers on its stop-and-frisk policy, to prevent unconstitutional checks of people on the street.

Former New York Civil Liberties Union director Norman Siegel said the department's training guide, patrol guide and a June NYPD stop-and-frisk training class for new officers does not clearly define the conditions under which an officer has a legal right to frisk a citizen.

Both the NYPD Patrol Guide and Training Manual state that officers can frisk someone if they reasonably suspect they or others are in "danger of physical injury." Officers are also instructed that if they reasonably suspect a subject "has, is or is about to commit a violent crime -- officer may frisk," according to Siegel.

In a New York Daily News video package on the June stop-and-frisk training class played Thursday by Siegel, an NYPD inspector states that if an officer suspects someone has committed or is about to commit a crime, the person can be stopped and "you can conduct an investigation, if necessary, we can frisk ..."

Siegel said such language "departs from the standard" contained in a key U.S. Supreme Court ruling in which "the magic words are ‘armed and dangerous.'" He would like to see that key phrase added to the city's training literature.

The 1968 Supreme Court ruling Terry v. Ohio said that an officer must have reasonable suspicion that the person has committed or is about to commit a crime to stop and question someone. To frisk, there must be a reasonable suspicion that the person is "armed and dangerous," the ruling said.

NYPD spokesman Paul Browne declined to comment.

In a letter to Mayor Michael Bloomberg and Police Commissioner Ray Kelly, Siegel urged the department to "sharpen and correct" the language it is using. The letter was co-signed by a state senator, two retired judges, a former Atlanta police chief and a Harvard sociology professor.

He said the training that young officers are receiving are leading to unconstitutional stops and frisks.

"People out in the street understand that they are being stopped when there is no criminal activity afoot, and they are being frisked when there is no bulge" that might indicate a weapon hidden in clothes.

In May, the NYCLU released an analysis of the NYPD's stop-and-frisk statistics that showed a dramatic rise in the number of stops in recent years.

A federal judge granted class-action status later in May to a lawsuit brought by the Center for Constitutional Rights on behalf of four black men who said they were racially profiled by officers who stopped and frisked them without cause. The issue has become a factor in next year's mayoral race.

NYPD officials said last week that police stops had dropped 34 percent from April through June of this year, attributing the drop to better training of young officers.

(Editing by Philip Barbara)

(This story was corrected in the second paragraph to show that Siegel is former director)