Some scars from the bomb blast are easy to see: glass fragments tore Sgt. Kassim Madloul Shinjar's left ear and right hand; the Iraqi policeman still clings to the bloodstained shirt he was wearing that day.
But other scars remain hidden, and show how violence waged by Iraqi resistance fighters against US occupation forces - and Iraqi "collaborators" - is undermining efforts to restore calm.
Sergeant Shinjar survived. The chief of Karbala's traffic police and his deputy - both passengers in the car Shinjar was driving - were killed by the car bomb on Dec. 27.
Today a dilemma gnaws away inside Shinjar's mind: Is the risk of being targeted as a collaborator worth the satisfaction of helping your community in the aftermath of war?
"I haven't decided until now - maybe I will come back; maybe not," says Shinjar, beginning to tremble, as thoughts of ending a 16-year career as a traffic cop mix with memories of the explosion that killed his closest colleagues.
Shinjar's car bomb was just one of four that rocked Karbala that day. That violence is killing an increasing number of Iraqi policemen, who walk the front lines of the US occupation. Two more policemen were killed and three wounded thursday, in a drive-by shooting at a checkpoint west of Baghdad.
"Our work is humane. Sometimes people give us flowers, so I don't understand why they attack such a place," says Shinjar, his eyes glistening with emotion. "I can't express what kind of human being would attack us - they are not human beings."
Shinjar's dilemma is shared by the growing ranks of Iraq's police forces. Government sources indicate at least 280 police have been killed nationwide since the fall of Baghdad in April, 2003.
In the capital itself, police officials say that 60 have died and 367 were injured between May 2003 and Jan. 9. During the Saddam Hussein era, one or two lost their lives each year.
Shinjar's example is a case study in how terrorism works in Iraq, and how a single blast can have corrosive effects. He was among the first in Karbala to present themselves for duty to the new US authorities, after the spring 2003 invasion swept north over this holy city.
He says his favorite time has always been the start of the school year because "you feel you serve the people, to help kids cross the street. I feel so proud, so useful." Shinjar even kept a patrol car at his house during the war, to protect it.
But now Shinjar feels doubt.
"All the neighbors have come to visit and support me, so I feel I want to come back to my job, to be happy, that I need my job," says Shinjar. "My father and family ask visitors not to talk about it. I try to forget, watch CD movies and watch television."
That spell disappears whenever the door slams, sparking a memory that he says takes him right back to the fear. Shinjar says he is still undecided about returning, because - like many police in Iraq today - his professional job is seen through a political lens.
"All of us reject the occupation, as citizens and as policemen," says Rahman Mushawer, spokesman for the Karbala Police. "But there is an international agreement, a promise that the occupation will end this year. We trust [the Americans] and their promises. We don't think we are collaborators."
Still, some of Karbala's 2,000 regular policemen - like local units around the country - have been fitted with new bulletproof vests in recent months.
And each day, the Karbala town council and police must confront the opinion of the Iraqi insurgents, who see them as sellouts. Six Iraqi police officers and six coalition troops - four from Bulgaria, and two from Thailand - were killed Dec. 27, in an assault that combined attacks with four suicide car bombs, mortars, and grenades across Karbala.
Some 37 coalition soldiers were wounded, along with 135 Iraqi police and civilians, in the most serious attack to date in south-central Iraq. The Polish general in command there called it a "coordinated, massive attack ... intended to do much harm."
Shinjar saw the car bomb in his rearview mirror just moments before it went off: the suicide bomber drove an official-looking four-wheel drive, and followed Shinjar's car past security checks and inside the protective barrier.
It went off exactly in front of the town hall and police station, near where some children were playing soccer.
Shinjar says his leather police jacket helped save him - the cotton shirts of his colleagues were incinerated. "When I got out of the car, I didn't know if I wanted to walk, or fall to the ground," he recalls. "I didn't know if I wanted to laugh or cry. I was crazy."
The 20-foot-wide crater in the asphalt is only now being filled with dirt. The verge of the road and sand-filled six-foot-thick blast barriers remain blackened and disfigured by the heat and force of the detonation.
The window curtain in Mr. Mushawer's office is spread with holes, pierced with shrapnel and broken glass.
"We never felt weak," Mushawer insists. "At the moment of the explosion, all of us here - even those injured - insisted on staying until everything was calm. The building was damaged, but we stayed that night, and the next day people came as normal. Some even came early."
But Shinjar didn't return for the first time until Wednesday, when his brief visit was riven with emotion.
"This was my first day to go back, and I so hesitated to go. When I went, I wanted to leave - especially when I saw the banner to the old chief, and I began crying deeply," Shinjar says.
Those weren't the only tears that day. Colleagues had two reactions. "Some expressed their sorrow; others took me to an office, brought me juice, and started joking and kidding with me," Shinjar says. "Then someone entered and began to cry, and I forgot everything and broke down."
After the bombing, spokesman Mushawer says that Karbala citizens "came to see that we had survived, and to confirm feelings of sympathy." They demonstrated against the attacks and sent letters of support; local sheikhs came to "insist that we will work with you, we will protect you - we need you to stay." That morale boost is part of a broader shift in popular Iraqi thinking about the police.
Like most police units in Iraq, perhaps 90 percent of Karbala's force are cops who did the same job under Hussein. Though taking small and large bribes were part of daily life, officers argue that they were often seen as a professional force, and not the despised enforcers of Hussein's security and intelligence organs.
"The end of the last regime caused the collapse of all institutions in Iraq, so from that point, the police began to carry on their shoulders the severe responsibility of protecting the people and their property," says Mushawer.
"People are not fed up with the police - they know they are here to protect the people and serve the city," says Adnan Awaz, deputy head of the Karbala town council. He says the insurgents are a small but vicious and disruptive minority, and that the Iraqi police are accepted by most others.
"The open-minded Iraqis think the US and American forces do them a favor, by saving them from the Saddam regime," says Mr. Awaz. "In every transition period, there are some victims who find martyrdom. The Iraqi people gave many martyrs - and [may have to] sacrifice more in the future."
The insurgents, whom police call "terrorists," are "using the space created by the insecurity" to target coalition forces and the Iraqis who work with them, says Lt. Col. Saad Khodayar Abbas, the new traffic police chief in Karbala.
He and his force routinely receive threats, but so far there has been "no action," says Colonel Abbas.
"Yes, my family worries like any family, when one goes out and does something. They worry until I come back [each day]."
Shinjar's family worries, too, as he recovers at home.
"Even if I do not go back [to the police force], I will get a new job that serves the people," says Shinjar. He smiles widely when asked if the "terrorists win," if he doesn't go back to being a traffic cop.
"I don't think so, because these terrorists are not human, to injure kids, and kill innocent people," Shinjar says, before making a bold prediction: "We [Iraqis] will put an end to terrorism in Iraq, because Iraqis are brave people."