Max M. Houck, Ph.D., Director at the District of Columbia Department of Forensic Sciences, is photographed on December 18, 2012 in Washington, D.C. (Ricky Carioti/WASHINGTON POST)

WHAT’S THE point of spending millions of dollars on a crime lab if people don’t trust its findings and won’t use it? That is one question D.C. officials should be asking in light of the unsettling revelation that the U.S. Attorney’s Office has stopped sending DNA evidence to the new Consolidated Forensic Laboratory because it claims there have been serious mistakes. Far more than money is at issue: Forensics plays a key role in determining the guilt or innocence of crime suspects. The concerns of federal prosecutors must be investigated and the integrity of the lab assured.

In January federal prosecutors stopped sending evidence for DNA testing to the crime lab, which is operated by the District’s Department of Forensic Sciences, opting instead to pay for tests at outside labs. The move, as The Post’s Keith L. Alexander reported, came after an outside expert, in a routine review of evidence for an upcoming case, found errors in the interpretation of test results; a subsequent review of 116 cases by two nationally known experts found what federal prosecutors characterized as critical errors in analysis.

Officials who operate the lab, housed in a $220 million state-of-the-art facility that opened in 2012, have defended their work, arguing that differences among experts over interpretation are not all that unusual in the scientific community. “It’s like a financial planner doing a financial assessment of someone’s net worth in U.S. currency and in Japanese yen. They’re both correct, just different measurements,” said Max M. Houck, director of the forensics department.

The concerns of federal prosecutors cannot be so easily discounted. Differences in interpretation of DNA data can determine whether a person goes to jail. Indeed, it’s hard to imagine why U.S. Attorney Ronald C. Machen Jr. would want to create so many problems for his office — notifying defense attorneys, calling cases into question, incurring additional expense — if he were not convinced there was cause for real concern. Such caution on matters that could lead to false convictions or criminals not brought to account is commendable.

Mr. Machen has retained a panel of experts to do a review that will include cases involving DNA analysis performed by the city lab that led to convictions. Another step in the right direction is the decision by Mayor Muriel E. Bowser (D) to have a separate audit that will be conducted by independent scientists recommended by the city lab’s accrediting agency. These are complex issues, and tension between law enforcement and independent crime labs is not unusual. But it is in everyone’s interest to settle the questions that have been raised about the D.C. lab and instill public confidence in its work.