A dirty cop is a danger to us all. That's why the case of Joseph "J.J." Jennifer, the 13-year veteran of the D.C. police department who was found guilty last week of possessing the illegal and dangerous drug PCP, bears close watching.

It was Jennifer who, on the evening of July 6, 2002, drove Dawn Rothwell, her friend Teresa Cole and Jennifer's friend Sylvester "Ves" Webb to a drug-infested area in Southeast Washington, where Dawn purchased a dipper, or a cigarette laced with PCP. It was Jennifer who drove them back to Dawn's apartment, where he witnessed the drug being consumed by Cole, Webb and Dawn. And it was Jennifer who was one of the last people to see Dawn alive before her body went over the railing of her 12th-floor apartment at 800 Southern Ave. SE in the early morning hours of July 7, 2002.

In January 2003, then-D.C. chief medical examiner Jonathan Arden told me that he had ruled Dawn's death an accident based on the "absence of evidence of a struggle or foul play" and on the basis of police interviews with unnamed people who were in Dawn's apartment the evening before her death ["How Did Dawn Rothwell Die?" op-ed, Jan. 25, 2003]. Two of those unnamed people, we now know, were Joseph Jennifer and his friend Sylvester Webb.

Notwithstanding the medical examiner's ruling, I was told this week that Dawn's case has not been closed. In response to my written inquiries, Channing Phillips, spokesman for the U.S. attorney's office for the District of Columbia, wrote that Dawn Rothwell's death "is still under investigation by our Office. Now that the trial of Jennifer is over, we plan to meet with the family members in the very near future."

As well they should. There are plenty of loose ends to tie up. Let's start with Jennifer. Had he done what a good police officer would do on the evening of July 6, Dawn Rothwell would still be alive -- a point well made by Assistant U.S. Attorney Steven Kaufman during the drug trial. There's more to be learned about Jennifer's behavior that night. Consider the testimony of D.C. homicide Detective Anthony Paci, a government witness in Jennifer's non-jury trial.

Paci said he had worked with Jennifer for nearly 10 years in the police department's 4th District in Northwest Washington and considered him a friend. Paci testified that he had received a call about a woman being found "laying in the grass" behind a building at 800 Southern Ave. Paci said he went into her apartment and found Webb alone, sleeping on a cot, and woke him up. He said Webb told him he was unaware that someone had fallen to her death. Paci said: "We asked him who was in the apartment that night and he named a police officer who he called 'J.J.' " Paci said he knew a "J.J." when he was with the 4th District and gave his name as Joseph Jennifer. Webb confirmed that was the person. After he returned to the violent crimes branch, where he worked, Paci said, detectives discussed who would go pick up Jennifer, and Paci volunteered because he knew Jennifer.

Paci said he and homicide Detective Steve McDonald went to Jennifer's house. Jennifer greeted them with alcohol on his breath. Paci testified: "We stepped inside his house, you know, and I explained to him that I'm investigating a death and his name came up in it and I want to talk to him about that. And I asked him if he had met any females the night before, and he said yeah. . . . He said yes, and I said, 'Do you know their names?' He said, 'I just met them,' through a friend of his. And I said, 'Well, one of them is dead.' And he said, 'Wow, we smoked some dippers and fall of the building and jumped off the building.' " The transcript may not be entirely coherent, but it certainly is curious.

When asked by the prosecution whether he had mentioned anything about the dipper to Jennifer, Paci said, "No. So, you know, at the time, you know, when he made the comment, I was kind of shocked behind it, because I didn't mention anything about it. And so I said, 'Well, look, that's what we're here to talk about, so come to our office and speak with them.' "

Details of subsequent police interviews with Jennifer have not been publicly disclosed, but Phillips confirmed that Jennifer was interviewed at length by the police and that prosecutors are privy to the results. Phillips, in response to my inquiry, said that the U.S. attorney's office has not interviewed Jennifer "because he had a Fifth Amendment privilege arising out of the PCP charge."

And now that the trial has ended?

Let's turn to Webb, possessor of four convictions, who said he was asleep at the time Dawn Rothwell went over the balcony.

As the prosecution observed during Jennifer's drug trial, there were other moments during which Webb "conveniently" claimed that he had passed out as a result of a high level of intoxication. Superior Court Judge Craig Iscoe made a similar observation in his summation: "[Webb's] recall seemed to be extraordinary for someone . . . as intoxicated as he described himself. And yet he did seem at various important parts to have been passed out and therefore avoiding examination on critical issues."

Reflect on the judge's and the prosecution's thoughts on Webb's credibility as you consider his claim to have been asleep as Dawn fell to her death. Reflect, too, on the behavior of Joseph Jennifer, who told Paci that he went to Dawn's apartment that evening to "get his freak on" or "have sex."

Dawn's mother, Barbara Rothwell, wrote in a Sept 10, 2002, letter to Police Chief Charles Ramsey (with copies to Mayor Anthony A. Williams and D.C. Del. Eleanor Holmes Norton): "I know my daughter did not jump from her balcony. Chief Ramsey, please don't let this get swept under the rug because one of your officers was involved."

Chief Ramsey, are you listening?