Karen A. Kelsey could not believe the results of the paternity test she had requested in applying for child support. She was convinced that Derrick E. Pumphrey was the father of her 7-year-old daughter. Line after line, the genetic codes declared she was wrong.

Angry and confused, Kelsey insisted on a second test. It concluded with 99.99 percent certainty that Pumphrey had indeed fathered her daughter.

The contradictory outcomes raise concern about impropriety and mismanagement in the genetic testing that the District uses in thousands of child support cases, experts and city officials said.

Genetic tests are a cornerstone for the legal system's handling of paternity issues, and the process is considered so foolproof that the results are accepted almost automatically in court, where judges consider any uncertainty or error unacceptable. Kelsey alleges that she was a victim of fraud, and authorities are investigating to determine what happened.

The sample collector who handled the two tests in Kelsey's case was dismissed this month after Kelsey accused her of manipulating the results of the first test by substituting another man's genetic sample for the father's. The collector denied any impropriety.

But this was not the first time that the private contractor hired by the city to do the testing ran into trouble. In April, another collector was fired after he left dozens of saliva swabs languishing for months in the testing room at D.C. Superior Court, even though they were supposed to go to a Michigan laboratory for DNA analysis.

"When we see two tests with completely opposite results, it concerns the court," said Lee F. Satterfield, presiding judge of Family Court, the Superior Court division that oversees child support matters. "It obviously implies something improper that's going on."

In an interview, Satterfield expressed alarm that the city did not promptly tell him about the conflicting results in Kelsey's case. The judge said he did not know of the matter until a reporter contacted him last week.

Questions about the integrity of the process could affect other cases, he said. Last year, the court handled 13,061 child support cases, including 2,203 new or reactivated paternity claims.

"If they have a sample collector who they are investigating to determine whether or not there were any improprieties going on in taking samples, we need to be notified, and we need to be notified of the time period in which this person was giving the tests," Satterfield said.

The District's office of the corporation counsel, which runs the child support program, said it launched an internal investigation this month into the testing problems and could forward the matter for criminal prosecution. The office also referred Kelsey's case to the D.C. office of the inspector general for a separate investigation.

Corporation counsel officials released a statement last week that said, "We encourage anyone with relevant information to bring it to our attention."

The District's Child Support Enforcement Division is among the poorest performing in the United States, according to national measures. In July, the U.S. Department of Health and Human Services warned that the District could lose millions of dollars in federal funds because it failed on three performance indicators and could not demonstrate that its data were reliable. In 2000, the District made collections in 12 percent of its 128,000 child support cases, compared with the national average of 42 percent.

Michael E. Barber, a former chairman of the American Bar Association's family law section, said the District's testing problems stand out in a normally fail-safe field. Since the mid-1980s, he said, DNA analysis has become the nationally accepted standard for parentage testing, and lab errors are extremely rare.

"The system would break down if we did not have reliable, accurate testing," said Barber, who ran the child support program in Sacramento for 20 years.

Experts said they were aware of few examples nationwide of actual corruption. In 1995, a sample collector was jailed and fined in Charlotte after she was convicted of taking $500 from a man to rig his blood test so that he could avoid paying child support.

Kelsey, a 29-year-old bank employee and single mother with one child in second grade, described her experience as an "ordeal" that cost her time, money and emotional energy.

She applied for child support in December 1999, when her daughter was 4. Nearly 2 1/2 years later -- on May 14 -- she got her first day in court after the District served Pumphrey with a summons. Pumphrey contested the paternity suit, and Magistrate Judge Hugh O. Stevenson ordered that a genetic test be conducted the same day.

A few weeks later, the results came back: Kelsey's daughter and Pumphrey did not share genetic markers in nine of the 12 chromosomal "addresses" examined. Two or three exclusions are enough to disqualify an alleged father.

Kelsey said she was crushed but did not lose hope. She said she raised concern about possible fraud to the child support division's testing coordinator, Monica R. McCauley. McCauley advised her to get a second, privately administered test, Kelsey said, an option she viewed as unrealistic.

At a follow-up court hearing July 9, Kelsey disputed the test results and asked the judge to order a second test. Kelsey said Stevenson predicted that the results probably would come back the same and that he then would dismiss her case.

"No one believed me, and that was very frustrating and humiliating," Kelsey said.

Although the first test was free, Kelsey had to pay $141 for the second test.

This time, Kelsey said, she left nothing to chance. She asked Stevenson to have the test monitored. He declined but ordered that Pumphrey, Kelsey and her daughter give samples at the same time, which had not been done in the first test. In the testing room, Kelsey would not sign an authorization form until she saw the collector take Pumphrey's sample, his fingerprint and a photograph. She brought a disposable camera to record the process. She even tracked the envelope in which the samples were mailed to the contractor's lab in East Lansing, Mich.

She also hired a forensic document examiner to analyze Pumphrey's signatures on two court documents and his supposed signature on an authorization form for the first test. The examiner concluded that Pumphrey did not sign that form, Kelsey said.

Kelsey got the second test's results in August. At a Sept. 25 hearing, another magistrate judge accepted them as proof of Pumphrey's paternity and awarded Kelsey $174 every two weeks in support.

Copies of the two sets of results show that a photo of Pumphrey was attached to forms for both tests. But the genetic markers for the alleged father on the two tests are different. Because each collection of markers is virtually unique, the samples could not have come from the same man, according to scientists.

In an interview, Pumphrey, 36, said that he provided the samples used in both tests and that he was not aware of any irregularities. He said he could not explain the contradictory results and was willing to start paying support.

"I don't have a problem taking care of any of the kids who are mine," he said.

The sample collector who handled Kelsey's tests, Shiral L. Burnette, was a $12-an-hour temporary employee who worked full time at the Superior Court site from May 2 to Oct. 3. In an interview, she said she remembered doing a second test in Kelsey's case. Burnette said she never mishandled the samples.

"I wouldn't want anyone to do me like that," Burnette, 28, said. "I have three children of my own, and I take care of two of my cousins."

The contractor that had done the District's genetic tests since 1998, Lifecodes Corp., was bought in December by Orchid BioSciences Inc., based in Princeton, N.J. The District pays about $70,000 a year for paternity testing.

Keith W. Brown, the senior vice president at Orchid who manages its paternity testing business, said city officials cited an "allegation" in requesting Burnette's removal. According to Brown, city officials "agreed that there is absolutely no proof at all" that Burnette did anything wrong. If a false sample was submitted in the first test, he said, it was done without Burnette's knowledge.

Orchid told the temporary employment agency that placed Burnette, District-based NRI, to replace her because of "two errors in record-keeping related to the presentation of identification by those being tested," said Robert Mulberger, the agency's president. The company put another temp worker in the job.

But Orchid had been having problems even before Burnette joined the company.

The previous collector, an Orchid employee named Michael Smith, was fired in April after he left dozens of samples at the testing site and failed to send them to the lab, according to city and court officials. Smith could not be reached for comment.

At the court, Satterfield said he learned of those delays early this year after a judge complained of waiting months to receive results from a test in one of her cases. Test reports usually take four to five weeks to complete. Satterfield said he met with Orchid officials and believed the problems were resolved when the company fired Smith and offered to take new samples in the delayed cases.

Peter J. Lavallee, a corporation counsel spokesman, said he knew of 13 cases affected by the apparent lapses, 12 of them District child support cases. New samples were collected in the dozen cases, he said. Along with administering court-ordered tests, Orchid's testing room at the courthouse offers private paternity tests.

Sources said the District is waiting for a fuller explanation from Orchid in Smith's case. Asked about that, Orchid's Brown said, "You could get sued for anything in this country. We choose not to divulge that information."

Brown said relations with the District have deteriorated to the point where the company offered to terminate its contract when it expired in March. Instead, District officials confirmed, the contract has been extended for a year.

"We're pouring gasoline on a fire," Brown said. "I really don't want to service an agency that has such low confidence in the services provided. That's not good for my business at all."

Meanwhile, the testing continues. The sample collector's position is not highly skilled, the company said. Burnette said she was trained by watching Smith do the job for a few days, and the current collector, Tia Evans, said Burnette showed her how to do it.

Brown defended his company's decision to use temporary workers, saying, "If it's a mouth swab that's being collected, it's about as difficult as brushing your teeth."

Staff researcher Bobbye Pratt contributed to this report.