MICHAEL MORTON was set free last month after spending 25 years in a Texas prison for a murder he did not commit. Mr. Morton would still be languishing behind bars had his lawyers not discovered new DNA evidence that incriminates a man with criminal convictions in several states.

The extraordinary outcome of the Morton case and the pivotal role played by DNA evidence appear to have gone unnoticed by a different set of Texas prosecutors — those handling the case of Henry W. Skinner, who is scheduled to be executed Nov. 9.

Mr. Skinner was convicted in 1995 of murdering his girlfriend and her two grown children. But key pieces of evidence were not tested, including a knife that might have been used in one of the murders and scrapings from the fingernails of one victim that could contain the killer’s DNA. Mr. Skinner argued that testing this evidence could prove another man committed the crimes. He won a victory this spring when the Supreme Court ruled that he should be given the opportunity to persuade a court that testing should be done.

Since then, Mr. Skinner has pressed his case in state and federal courts in Texas — and the state has aggressively pushed back. Prosecutors argue Mr. Skinner has not established that the new DNA tests will probably exonerate him. They say revelations that turn in Mr. Skinner’s favor would not erase the existing evidence that points overwhelmingly to his guilt.

But how is Mr. Skinner to prove that tests will clear him, and how can prosecutors be so sure that no set of results could cast doubt on the conviction unless the tests are performed?

The state court judge overseeing the case should put the execution date on hold and order the testing. We oppose capital punishment, but for all anyone knows, the results could definitively prove that Mr. Skinner is guilty. The state should want this level of proof before it puts a man to death.