The murder trial of Chicago Police Officer Jason Van Dyke starts in earnest Monday with opening statements, just a few weeks after a police officer in suburban Dallas was convicted of the murder of an unarmed teen.

While that timing might suggest police officers frequently face murder charges, fatal police shootings resulting in the most serious charge are rare — and convictions almost unheard of.

Van Dyke is the only police officer to be charged with murder in the state of Illinois since 2005, according to a database maintained by former cop and Bowling Green State University law professor Philip Stinson. The last time a Chicago cop was charged with murder while on duty was 1968. That officer was eventually convicted and sentenced to 14 years in prison.

Nationally, only 93 officers have been charged with either murder or manslaughter for an on-duty shooting in the last 13 years, and only 33 have been convicted, according to Stinson’s data. And only two of those officers, including Texas police officer Roy Oliver’s guilty verdict last month, were convicted of murder. The rest were found guilty of lesser charges, like involuntary manslaughter or negligent homicide.

Fired Balch Springs Police Officer Roy Oliver testifies in his own defense during his murder trial last month in Dallas. He was convicted of the murder of an unarmed teen, 15-year-old Jordan Edwards. | Rose Baca/The Dallas Morning News via AP, pool

In 2017, a year in which the Washington Post compiled a total of 987 fatal police shootings, six officers were charged with murder or manslaughter.

Charges are unusual in police shootings because the bar is high to bring charges against law enforcement officers, Stinson said in a recent interview. The law allows officers to use deadly force when they are in “reasonable fear” of their own safety, Stinson said, and convictions are rare because judges and juries seem to believe police when they say they felt threatened.

“They’re generally reluctant to second-guess a split-second decision made (by police officers) in potentially dangerous street encounters,” Stinson said.

In the nearly three years since Van Dyke was charged with first-degree murder, official misconduct and 16 counts of aggravated battery — one for every shot he fired at 17-year-old Laquan McDonald — his lawyers have been laying the groundwork for a self-defense case. They are planning to assert that his actions in the 2014 shooting were consistent with the law and his police training. It’s the same case officers across the country have made when facing similar charges.

Van Dyke decided last week he will proceed with a jury of eight women and four men rather than have Cook County Judge Vincent Gaughan hear his case. One of the jurors, a Latina, is applying to be a Chicago police officer and has wanted to be a cop since she was 12.

In 42 cases in which the officers didn’t get convicted, 22 were decided by juries. Judges either acquitted or dismissed charges in 13 other cases, and seven cases didn’t proceed for other reasons, including the prosecutor dismissing the charges.

The 33 guilty verdicts against officers are a near-even split: 17 were found guilty by a jury; 16 entered guilty pleas. None of the officers convicted was found guilty in a bench trial. Out of the 93 officers across the that have faced charges since 2005, 18 cases are pending.

The above data is based on when officers were charged with the crimes.