Several episodes of alleged murder by U.S. soldiers in Iraq are making headlines.

In the most sensational case, a half dozen serving and former troops are charged with raping a teenager in Mahmoudiya, then killing her along with her family. In another awful tale, a unit of Marines allegedly murdered 24 civilians in Haditha to avenge a comrade's death.

These horror stories — with the moral and political questions they raise — have grabbed our attention. But they are exceptions: Despite the stress on U.S. soldiers of repeated tours of duty in a misconceived war, such murders are presumably rare.

What has remained under the radar screen is the numbers of Iraqi civilians accidentally killed by coalition troops.

Americans have scant idea of how often such episodes happen. The Pentagon releases no figures on Iraqi civilians killed by U.S. fire. Each of these unsung civilian deaths creates Iraqi enmity toward U.S. troops from the friends, family and tribe of the dead.

Just over a year ago, my translator, Yasser Salihee, was shot dead by an American soldier. Salihee, a 30-year-old medical doctor and aspiring journalist, was working for Knight Ridder News Service to make extra money. He was driving home after a haircut when a U.S. sniper mistook him for a potential car bomber. He couldn't stop in time and was shot between the eyes. (Jacki Lyden of National Public Radio broadcast a detailed investigation of his death on the June 23 "All Things Considered." The transcript is at go.philly .com/yasser.)

I arrived in Baghdad right after Salihee died and told his story to several Iraqi officials. The reactions were astonishing. Iraqi Vice President Adel Abdel Mahdi told me an elderly friend of his had just been shot dead by U.S. soldiers. Kurdish parliamentarian Mahmoud Othman told me that he knew of 10 civilians who had been shot dead by U.S. soldiers. Iraq's ambassador to the United Nations, Samir Sumaidaie (recently appointed ambassador to the United States), complained bitterly to reporters that U.S. Marines had killed his unarmed 21-year-old cousin.

These cases came to light because the victims were well connected. But Salihee's death was investigated only after pressure from Knight Ridder. No one knows how many similar cases are never even reported. And armed civilian contractors there are notorious for shooting at Iraqi civilians with impunity.

American soldiers are understandably jittery at checkpoints or house searches. They have to make instant decisions in threatening situations. But until recently, procedures at checkpoints and roadblocks have often been murky. Salihee would be alive if there had been a roadblock warning him to slow down.

When I wrote about his unnecessary death, I received e-mail accusing me of undermining the military and coddling terrorists. The writers just didn't get it. Mistaken shootings of Iraqi civilians by U.S. troops are not just terrible tragedies; they also endanger American lives.

The current U.S. ground commander in Iraq, Gen. Peter Chiarelli, who took over in January, does get it. In March, says the New York Times, he told his troops: "Every time we shoot at an Iraqi in this culture — a culture of revenge, a culture of honor — we stand the chance of taking someone who is sitting on the fence" and pushing him toward "the terrorists and the fighters."

Chiarelli is trying to establish clearer rules to avoid confrontations between Iraqi civilians and U.S. soldiers — a much-overdue improvement. According to recent statistics compiled by the U.S. military in Baghdad, the number of Iraqi civilians killed at checkpoints, roadblocks or alongside convoys dropped to an average of one per week in 2006, down from one a day during 2005. Those figures seem very low, especially since many such deaths go unreported.

The British researchers at Iraq Body Count — www.iraqbodycount.net — which tracks Iraqi civilian deaths, calculate from 38,843 to 43,272 Iraqi civilians have died since 2003 as a result of the coalition invasion and occupation, from all causes, including bombs, insurgent violence, crossfire, etc. Those figures don't break down the causes.

Last month, Iraqi Prime Minister Nouri al-Maliki decried the "regular occurrence" of violence by U.S. troops against civilians. Chiarelli's challenge is to get a handle on how many civilians are dying at the hands of U.S. soldiers and to get those numbers down.

Trudy Rubin is a columnist and editorial-board member for the Philadelphia Inquirer. Reach her at trubin@phillynews.com.