ON WEDNESDAY, OCTOBER 21, I saw a homeless man brutally attacked by a half-dozen young men. Thomas Lundahl was thrown against the entrance to the Portland Outdoor Store and punched several times before the men ran off.

Several people, myself included, placed 911 calls during the incident, and within minutes three squad cars were on scene at SW 3rd and Oak. I listened as Lundahl, the victim of the attack, told officers that he was on the corner distributing free postcards with drawings he'd done. He spent most nights under a bridge, he said. When asked how the attack started, Lundahl said he tried to intervene when the group of men attempted to steal a woman's iPod.

When the officer asked Lundahl if he wanted to press charges, he declined, even when told that another officer had stopped a group of men that may have been involved in the attack.

When I described what I saw to Mary Wheat, public information officer for the Portland Police Bureau, she told me it's standard to ask victims if they wish to prosecute in cases like this.

"The victim has to want to press charges," Wheat says of this case. Without a victim, "the district attorney can't take the case because there's no one to represent."

There are exceptions to that rule. Domestic violence cases are pursued regardless if the victim goes along with it or not. Same with cases in which a child is the victim. But despite their level of vulnerability, Wheat says the homeless don't fall under the same umbrella.

"We have to be very careful about the manpower that goes into a case when someone doesn't even want to prosecute," Wheat says.

The homeless are particularly vulnerable to assaults like the one I witnessed. More than 40 percent of Portland's homeless have sustained concussions from being attacked while sleeping. Nationally, there were 106 violent acts perpetrated against the homeless in 2008, according to the National Coalition for the Homeless. Twenty-seven attacks were fatal. In the Portland area, there were five recorded attacks against the homeless last year.

Tracking the attacks is made difficult by the fact that many homeless people don't have a phones or addresses. That not only inhibits initially reporting attacks, but also makes it difficult for officers to follow up on investigations, says Israel Bayer, director of Street Roots.

"We have heard that there are increasing attacks on homeless people," said Sally Erickson, homelessness project coordinator with the City of Portland. "The best thing we can hope for is for everyone to have a safe place to sleep at night."

Bayer says because of the difficulties in prosecuting crimes against the homeless, the police and those on the streets have developed a sense of apathy. The homeless may feel like it's useless to report violence, and police don't want to get into cases based entirely on hearsay.

But that's a mindset Wheat doesn't agree with.

"We deal with vulnerable people every day," Wheat says. "We can't force them to sign a complaint. We can't force them to come to trial."

When asked if the homeless should be a protected class like children or domestic violence victims, Wheat said that's not up to the police.

"That's a question for lawmakers," she says.