Washington ? Reformed after controversy in the mid-1990s, the FBI crime lab is dealing with new wrongdoing by employees that has opened the door for challenges of the lab’s science in scores of cases involving DNA and bullet analysis, internal documents show.

One FBI lab scientist, who connected suspects to bullets through lead analysis, has been indicted after admitting she gave false testimony, and a technician has resigned while under investigation for alleged improper testing of more than 100 DNA samples, according to records and interviews.

In addition, one of the lab’s retired metallurgists is challenging the bureau’s science on bullet analysis, prompting the FBI to ask the National Academy of Sciences to review its methodology, the records obtained by The Associated Press show.

FBI Lab Director Dwight Adams said detection of the problems illustrates that reforms are working.

“The difference is these are being caught and dealt with swiftly. Our quality assurance program is in place to root out these problems, incompetence and inaccurate testimonies,” Adams said in an interview. “These weren’t fortuitous catches; they were on purpose.”

Defense lawyers are already mounting challenges in high-profile cases handled by the two employees and are questioning the FBI’s project to build a national DNA database that will help law enforcement identify suspects based on their genetic fingerprints.

“We all have assumed the scientists are telling the truth because they do it with authority and tests. And as a result FBI scientists have gotten away with voodoo science,” said Lawrence Goldman, president of the National Association of Criminal Defense Lawyers.

The Justice Department’s internal watchdog is investigating FBI lab technician Jacqueline Blake for allegedly failing to follow proper scientific procedure when analyzing DNA in at least 103 cases over the past few years, officials said.

The officials said they have found that the technician failed to compare the DNA evidence with control samples, a required step to ensure the accuracy of tests. Blake resigned from the FBI lab recently.

Blake’s work has become an issue in a prominent case in New Jersey, where five police officers are challenging blood evidence she analyzed that was used to convict them of federal civil rights violations in the death of a prisoner.

FBI officials have already taken steps to protect the national DNA registry in light of the allegations against Blake and separate revelations of problems in DNA analysis at the Houston police crime lab.

In Blake’s case, 29 DNA samples that she placed into the database were removed and are being reanalyzed. The review so far has not found any instances in which her DNA analysis was inaccurate, and those samples have now been re-entered, Adams said.

In addition, FBI officials recently banned the Houston police lab from entering new DNA samples into the national registry. Judges in the Houston area have requested a grand jury investigation into that lab’s practices.

The FBI made widespread changes in the mid-1990s after its lab was rocked by a whistleblower’s allegations and an investigation that found shoddy science by several lab examiners. AP reported last month that Justice officials have identified about 3,000 cases that might have been affected by those earlier problems and have let prosecutors decide whether to notify convicted defendants.