Displeased with slipshod detective work in the case of two Southeast Washington teenagers shot to death Monday, D.C. Police Chief Charles H. Ramsey dismantled the investigative team, pulling three detectives off the case and sending a lieutenant back to street patrol.

"There were some things that were missed that shouldn't have been missed," Ramsey said yesterday, of the crime scene Monday night in the 300 block of 37th St. SE. "People need to do these jobs competently not just some of the time, but all of the time."

Several miscues prompted Ramsey's decision, including the absence of detectives at the autopsies of Natosha Adams, 17, and Melissa Payne, 16, he said.

But the problems in the two-day-old investigation did not end there, Ramsey said.

"There were other things that veterans should not have missed. It was a combination of things," he said, without specifying what those mistakes were. But department sources said the chief fumed when he learned that shell casings found later had not been picked up on the first sweep of the crime scene Monday night.

Lt. Robert Tate, head of the 6th Police District's homicide division, was immediately transferred to the 3rd District, where he will be on patrol, Ramsey said. The three detectives will be reassigned to other cases in that district. Because they are not being demoted, Ramsey said, union rules prohibit him from naming them publicly.

The lieutenant is being replaced by Capt. Peter Newsham, and the new lead detective is Anthony Duvall.

Yesterday's actions were the latest in a string of demotions Ramsey has made this year. And it is not the first time the chief has heard horror stories about sloppy police work at crime scenes.

Two commanders were demoted to captains in the 4th District last month. In June, a detective was demoted to desk duty.

In October, an officer and a detective did not search a house where a female strangling victim was found, believing she had died of natural causes.

It was only after family members smelled a foul odor in the basement that police were called back and found the body of a second woman, shot to death.

Police later determined that the crime scene had been compromised.

Last month, a District cabdriver was found slain in his taxi, and police said the man had been shot to death. He had been stabbed multiple times.

In another attack on a cabdriver, police returned the taxi to the victim after their evidence search failed to find part of the assailant's knife that had been left inside.

To fight the possibility that the most recent slaying investigation would falter, Ramsey formed a task force, partnering D.C. police with three federal agencies.

The FBI has offered its resources and investigators; the Drug Enforcement Administration will help investigate whether there are any drug connections that may have led to the girls' killings; and the Bureau of Alcohol, Tobacco and Firearms will try to trace the bullets.

Although many successful homicide investigations rely on breakthroughs made in the first 24 hours, Ramsey said the trail of Payne and Adams's killers has not grown cold.

"We'll still be able to solve this," he said.

Jacqueline Adams, one of the dead teenagers' mothers, said she was immediately questioned by police and said she has no idea who would want to kill her daughter.

Still wearing the cherry-red pants her daughter gave her for Christmas, Adams left the apartment yesterday to make funeral arrangements, passing by a telephone pole that has become a memorial of teddy bears honoring the slain teenagers.

"Someone had to know they were coming home and be waiting there for them," said one of Natosha Adams's friends.

"I don't think they witnessed anything anyone would kill them for. They didn't live that life. And if they saw something, they couldn't hold it in. They'd tell everyone about it."