Seven years ago. Apartment Five. A depressing, one-room flop just east of the FEC railroad tracks in Hallandale Beach.

That cramped space with a floor out of plumb provided a final incongruent address for a 17-year-old runaway, miles from her suburban home in West Broward.

Marissa Elan Karp had wandered into circumstances far more horrific than those often imagined by parents worried that a wayward child might fall in with the wrong crowd. She became fatally entangled in a nest of killers.

Marissa was battered. She was shot in the chest. Her body was crammed into a plastic garbage bag, hauled to the Everglades and dumped into the L-28 Canal under Alligator Alley.

Discarded beer cans and mindless graffiti sprayed on concrete bridge pillars mocks the depravity of what a water district worker discovered there on Aug. 19, 2002. Perhaps her killers thought the death of some runaway teen would attract scant attention in South Florida, where the scores of unidentified young murder victims molder in eternal anonymity at the county morgues.

But Marissa, we learned that year, was among 393 foster children classified as missing from the Department of Children & Families' custody. The body, found floating like a bag of rubbish in the L-28 Canal, became a ghastly symbol of agency failure. It wasn't just murder. It was scandal.

Nor would the killers have calculated the obsessive determination of a father trying to keep his daughter's murder from fading from the public memory.

Despite the notoriety, seven years have passed with no arrests, no indictments. Officially, the death remains an unsolved murder. But that's not quite the case. Investigators know details. They know names.

Police know so tantalizing much about the kid's fatal encounter with a Bahamian drug ring operating in Broward County that Gary Karp has been driven to distraction waiting for an arrest. ``It has been seven years,'' the father said, his voice knotted with frustration. ``Enough already.''

Police have matched a gang member to DNA evidence scraped from beneath Marissa's fingernails. They have a statement from one of the men who tossed her body into the canal. They've interviewed witnesses who recalled gang members discussing the shooting and the shooter.

It's not enough. A source close to the investigation told me that the suspects in Marissa's murder and the cover-up and disposal of her body are so utterly tainted by criminal acts that they're nearly immune to the usual law enforcement squeeze tactics. What truth cops have gleaned from the investigation has been obscured by braggadocio and lies and denials and conflicting accounts. Investigators think they know who was involved, but they haven't yet sorted out the actual shooter from a mess of bad actors.

Nor have police recovered the murder weapon; probably tossed in the canal. And Apartment Five, which wasn't searched until more than a month after the shooting, yielded little in the way of evidence other than a bullet hole in the refrigerator.

There's another major complication: Names that surfaced seven years ago in the Karp investigation have since been linked to other brutal killings in Broward County, including the Nov. 12, 2006, roadside shooting of BSO Deputy Brian Tephford.

``When I saw on CNN that night that there was a manhunt for a [suspected] cop killer named Devon Ingraham, the hair on my neck stood on end,'' Gary Karp said.