DNA sequence and helix models, man in background (Digital Composite) (Chad Baker/Ryan McVay/Getty Images)

Widely used methods to trace complex DNA samples, bullets, tread and bite marks to criminal defendants fall short of scientific standards, limitations that federal prosecutors and judges should seriously consider before entering forensic evidence in trials, a presidential panel urged Tuesday.

The unanimous report by the 20-member President’s Council of Advisors on Science and Technology does not advocate banning testimony or putting limits on tools used for investigations.

But when it comes to evidence at trial, the report says, the Justice Department and federal judges should give greater weight to scientists’ view of forensic evidence, particularly in light of a landmark 1993 Supreme Court decision that ruled courts should act as gatekeepers and admit only “scientifically valid” expert testimony.

The council’s co-chairs said in an interview that scientists were not telling judges what to do. But they said they hoped the report would ensure the scientific reliability of forensic techniques used in thousands of cases each year.

“For a forensic science to be scientifically valid, you need actual, empirical evidence of its reliability and accuracy, period,” said Eric S. Lander, founder of the Broad Institute of Harvard and MIT. “Historically that hasn’t been the case.”

Lander and White House science adviser John P. Holdren co-chaired the council.

The report found that “feature-comparison” techniques that link a person or an item to a crime scene through bite marks or treads from shoes or tires fell “far short” of scientific standards and lacked “meaningful evidence” of their accuracy. The report concluded that evidence supporting firearms tracing was promising but needed more corroboration.

Analysis of high-grade samples of mixed DNA — where the DNA of up to three people may be in the sample — was “well-founded,” according to the report. But interpretation of more complex DNA mixtures currently was “not a reliable methodology,” the report found.

Overall, the lack of rigor in researching error rates and ensuring that forensic results do not rely on the subjective views of law enforcement experts “is a real and significant weakness in the judicial system,” the council said in a 174-page report that President Obama commissioned last year.

“Neither experience, nor judgment, nor good professional practices . . . can substitute for actual evidence of foundational validity and reliability,” stated the final report, which the White House provided to The Washington Post. “Expressions of consensus among practitioners . . . [are] no substitute for error rates.”

A Justice Department spokeswoman said there was “always a place for continued review,” but noted that DOJ had taken “unprecedented steps” in the last few years to strengthen forensic science and was “confident that, when used properly, forensic science evidence helps juries identify the guilty and clear the innocent.”

An FBI statement was directly critical of the report saying it “makes broad, unsupported assertions regarding science and forensic science practice” and conflates distinctions about levels of evidence that led to “troubling generalized conclusions about all forensic science disciplines.”

The pre-publication backlash among several law enforcement groups also underscored what is at stake.

In a Sept. 1 email alert, Matthew Gamette, director of forensics for the Idaho State Police and senior board member of two leading crime lab organizations, said the Justice Department had held a series of calls with prosecutors, law enforcement and lab officials, and that it “does not support or agree” with a testimony ban, and would provide “a packet of information to federal prosecutors regarding how to dispute this report in court.”

In later public statements, the National District Attorneys Association accused the council of “scientific irresponsibility,” and Jim Pasco, executive director of the Fraternal Order of Police, was quoted in the Wall Street Journal saying that the effort to overturn years of settled law over expert testimony posed “a threat to the public safety of our American citizens.” Pasco said Monday that he continues to hold that view.

The council report advocates that law enforcement “be precluded from using most forensic evidence in the investigation and prosecution of criminal offenses,” the DA association said, adding, “Adopting any of their recommendations would have a devastating effect.”

Nelson O. Bunn Jr., spokesman for the DA association, on Monday said the group stood by its statement.

Gamette said Monday that the Consortium of Forensic Science Organizations was withholding comment until it could review the final report.

The White House report adds to a critical 2009 report by a congressionally charted National Academy of Sciences panel that traced weak standards for crime labs, examiners, testimony and research in part to crime labs being under the control of law enforcement.

The new report makes more concrete and pointed recommendations to federal courts and Attorney General Loretta E. Lynch.

For instance, the White House report praised the FBI for research in recent years that established a reliable error rate in fingerprint examinations of better than 1 in 300 matches.

It recommended increasing the research budgets of the National Institute for Standards and Technology and the FBI to about $44 million a year to expand similar work and to develop automated systems to trace fingerprints, bullets and DNA mixtures, under a government-wide strategy set by the White House Office of Science and Technology Policy.

Lander, a leader in the human genome mapping effort, likened the challenge to the early days of DNA testing, when inconsistency among testing labs in discerning genetic profiles and declaring matches led a New York judge to bar results from court. That 1989 decision led to joint efforts by forensic and non-forensic scientists, including him, to produce what became a “gold standard” for DNA crime lab work.

But tension between law enforcement and scientists over what forensic analysis is scientifically sound and what needs more study has impeded reforms, according to some legal observers.

And some critics said the outcry that arose before the White House report was officially released has exposed those lingering problems.

If the forensic science community “is going to view it as an attack” when other scientists question their methodology, “it’s going to make it difficult to generate support from other scientists,” White House council member S. James Gates Jr., a theoretical physicist at the University of Maryland, said in an interview.