Two grand juries are investigating the Houston crime lab scandal. Reports are surfacing that the grand jury wants to extend the probe to prosecutors involved in the prosecution of cases that involved tainted evidence.

Reportedly,

this reflects an awareness of a possible conflict of interest that the prosecutors face in the scandal over the laboratory's DNA unit, which was closed down in January after a state audit found widespread flaws in its work, including sloppy record-keeping, misinterpreted data and evidence contaminated by water from a leaky roof in the laboratory.

DNA legal experts Barry Scheck and William Thompson testified before the grand juries last week.

In an interview that morning, Mr. Scheck said, "The grand juries are running away because the district attorney, they realize, shouldn't be conducting this investigation in the first place because he has such terrible conflict issues."

All 22 state court judges asked the District Attorney to recuse himself. He refused.

On Saturday, The Houston Chronicle reported that Mr. Rosenthal and several of his assistants had been subpoenaed to testify before one of the grand juries and that, in a letter, the grand jury's foreman had asked Mr. Rosenthal to recuse himself from the investigation. Mr. Rosenthal again declined.

Can prosecutors fairly investigate the use of evidence in their own cases? Are grand jurors or legislators capable of fairly making scientific judgments? What sort of investigation is best suited for identifying crimes or freeing those who are wrongfully convicted?

One prisoner, Josiah Sutton, was cleared in March after the DNA that had been used to convict him of rape, based on tests by the Houston laboratory, was retested.