Eighteen women claimed last week that Brooklyn narcotics policeman Charles Derosalia illegally strip-searched them, in violation of department rules that male cops can't force female suspects to disrobe. The Daily News reported that "if Derosalia is found guilty of the charges, he'll likely be fired."

He'll likely be fired. The fact is that cops who fail to protect or serve have a very difficult time actually losing their jobs.

Remember the off-duty cop who pulled a gun on a couple in an altercation in a Queens parking lot? He was found guilty in a departmental trial of taunting the couple with his gun and remains on the force after being docked for 30 vacation days.

Remember the officer from the Internal Affairs Bureau — the police unit that investigates corruption — who used threats and intimidation against a fellow officer in the hospital in an attempt to get the officer to drop charges against a friend? He was found guilty in a departmental trial, suspended for 60 days, and placed on probation.

It's not like it's impossible to get fired. If, say, you rob a perfume warehouse, like the three NYPD officers allegedly gone awry in New Jersey this year, you can get canned. Also, if you're wet behind the ears: Officers on probation during their first two years on the force can earn pink slips for relatively small infractions.

“If you use drugs you’ll definitely be fired, no doubt about that,” said Rae Koshetz, former NYPD deputy ­commissioner­ for trials, the top NYPD administrative judge. “If you commit a corruption offense — if you’re caught taking money — you’re finished. With other things there’s more discretion.”

Police trials are overseen by an administrative judge in a courtroom setting. Guidelines for punishment are in the city code, but judges have significant leeway. At the end of a trial, the head judge makes a recommendation to the police commissioner, who has veto power over discipline. Even after the commissioner signs off, the police officer in question can appeal to the New York State Court.

That was the case with a former counterterrorism detective who claimed that his positive drug test was due to pot-laced meatballs his wife made without his knowledge. His dismissal from the department was upheld in the State Court of Appeals in February.

The department tends to be more lenient with alcohol-related offenses, though that has caused some degree of controversy during a year with an unusual number of alcohol-related cases.

“These guys have guns,” said Peter Vallone Jr., chair of the New York City Council public-safety committee. “A DUI, in most cases, should be reason enough to remove someone from the force.”

Officers are always required to be “fit for duty,” but that is broadly interpreted. Four officers were disciplined this year for drinking and driving with between 30 and 60 days of suspension without pay. One officer was docked 40 days of pay for drunken harassment.

Two officers from the 32nd Precinct were killed while one was allegedly driving drunk in the Bronx in May. Other 2010 cases related to alcohol reportedly working their way through the police discipline and criminal-court systems include a cop who crashed into Tiffany’s, an officer who killed a preacher’s daughter, and one who hit and killed a Bronx grandmother.

The force, however, is sending a message that alcohol abuse will not get an officer fired. Consider the Brooklyn police officer who hit a parked car in Williamsburg during a 3 a.m. binge in 2008 and then fled the scene. He was found guilty in a departmental trial of driving while intoxicated. The discipline was suspension without pay for 40 days and one year of probation.

Koshetz said that judges take into account the rank, years of service, and past record of officers when deciding discipline. Insiders also say it comes down to connections. A good word from the right person can go far. Hence, the discipline against officers convicted in police trials of wrongdoing — lost vacation, being bumped down a rank, early retirement — varies wildly.

“If you’re not connected and you don’t know people, then you’re treated differently,” said Eugene O’Donnell, a professor of law and police studies at John Jay College of Criminal Justice. “It’s who you know. That’s the whole thing.”