Every year the National Law Enforcement Officers Memorial Fund (NLEOMF) releases figures on the number of American police officers killed in the line of duty. Last year the figures were particularly grim.

In 2010, 162 officers didn't make it home to their loved ones. That's a nearly 37-percent increase in line-of-duty deaths over 2009's total of 117.

There are two major causes of police fatalities in contemporary America: automobile accidents and malicious attacks.

Automobile accidents are the primary cause of untimely death in America. And you drive a lot more than the average citizen, so you're at risk of dying on the road. And very few of you wear seat belts on the job.

Among some officers it is gospel that wearing a seat belt can put you at a tactical disadvantage if you are shot at in your car. I have discussed this issue with some of the top tactical trainers in the country and every one of them has responded with a two-syllable word for bovine excrement.

But I know that's not going to convince some of you, so I'm going to ask you to consider the odds. How many times have you heard of a police officer being gunned down in his car because the officer couldn't get out of a seat belt? OK. Now ask yourself how many officers in your state have been killed in traffic accidents.

Researchers for the National Highway Traffic Safety Administration recently concluded a study analyzing 733 police crashes from 1980 through 2008. They found that at least 42 percent of officers killed in traffic accidents during the study years were not wearing seat belts. Last year 73 officers were killed in traffic accidents. Thus, the odds of you dying in a traffic accident are much higher than the odds of you being shot while restrained in your car.

So wear your seat belt.

Traffic accidents killed the majority of cops last year, but the statistic for malicious attack with firearms wasn't far behind. A total of 61 officers were shot to death last year, a 24-percent increase over 2009. And probably five times that many were shot at or wounded or saved by their body armor last year.

Some experts say the rise in malicious attacks on officers is the result of budget cuts and reduction in the number of officers on the street. Some say the cause is a more bloodthirsty species of thug that now makes up our criminal population. And of course, folks on the left blame easy access to guns and a "You're never taking me alive" desperation engendered in criminals by Three Strikes laws and other stiff sentencing guidelines.

But the real reason that so many officers are being killed by gunfire is revolving door justice. Since January 1 of this year, I know of at least three cases of officers killed or seriously wounded by people who shouldn't have been on the streets.

• Ohio deputy Suzanne Hopper was murdered by Michael Ferryman, a man who served time in a state facility for the criminally insane. This is just common sense, but I'm going to say it. We should keep tabs on guys released from hospitals for the criminally insane and that information should be available to all police dispatchers.

• Georgia State Trooper Chadwick LeCroy stopped a motorist because of a broken tail light. He was shot and killed. Gregory Favors has been charged with the murder. Favors has been in and out of jail so many times that it's staggering. He has been arrested 18 times, including a federal firearms conviction.

• Los Angeles County Sheriff's deputy Mohamed Ahmed was shot in the face by Nestor Torres. Torres, a documented gang member, was on parole for two felony convictions: shooting into an inhabited dwelling and firearms possession. Ahmed was patrolling with his training officer. The training officer killed Torres. So he will no longer be able to access the revolving door.

But how many other dangerous thugs are walking our streets? No one knows. And that's the problem. If we really want to save police lives, then we have to keep better tabs on dangerous parolees and other people who present a deadly threat to law enforcement and to society.

Related:

11 Officers Shot Over 24 Hours Causes Fear of 'War on Cops'

Four Detroit Officers Shot in Precinct Assault

Wash. Deputies Wounded in Walmart Gunfight

Indianapolis Officer Shot by Felon Fights for Life