In the face of opposition from the city’s law enforcement unions, the police department is seeking to use hair samples from officers as a means of testing for drugs, a method proved to be significantly more effective than the urine samples now in use, experts say.

Proponents of hair testing say it would more effectively prevent rogue officers from clouding the results of urine samples, which can be flushed of drugs within a matter of days. Such officers could endanger public safety and undercover operations.

Over the past three years, the department has been stopped from randomly testing officers’ hair on two occasions. The New York City Board of Collective Bargaining first banned it in December 2006 following complaints filed by the police unions, and, most recently, a Manhattan appeals court on March 13 banned random hair testing only a year after a state Supreme Court had established it as a new technology, ruling the department was entitled to use the method without negotiating with the unions.

Unlike urine testing, which provides roughly a 72-hour window, hair examination can provide detailed analysis of a person’s drug use for up to several months, the chairman of the Department of the Sciences at John Jay College of Criminal Justice, Lawrence Kobilinsky, said.

In an affidavit filed in state Supreme Court, the police department’s head of personnel, Chief Rafael Pineiro, said 14 officers tested positive for drug use during the first 16 months the department instituted random hair testing, a period that began in August 2005, while only one officer tested positive for drug use during the previous 16-month period.

The March 13 decision to stop hair testing, made by the Appellate Division, First Department, put a stay on the testing until the court has more time to consider the appeal.

“We are disappointed with temporary stay,” a senior counsel in the appeals division of the New York City Law Department, Julian Kalkstein, said in a statement. “However, we are confident that, when the Appellate Division has the opportunity to consider the appeal on its merits, it will find that the lower court properly ruled that the Police Department was entitled to use this test on all police officers and it was not a matter that was subject to collective bargaining.”

Patrick Lynch, the president of the city’s largest police union, the Patrolmen’s Benevolent Association, said the department should have stopped random testing before having its hand forced by the courts.

“The NYPD should have ceased the practice of testing police officers’ hair on January 31,” he said in a statement. “When it did not, the PBA, in cooperation with the [Drug Enforcement Administration] and [Sergeants Benevolent Association], filed a motion with the Appellate Division, First Department, to enforce the stay and to preserve the rights of its members.”