THE SUPREME Court no doubt made few enemies by affirming the conviction and death sentence of Tommy David Strickler, a Virginia death row inmate accused of the 1990 slaying of Leanne Whitlock. Ms. Whitlock was abducted from a shopping mall parking lot and later found with her head crushed. Mr. Strickler was clearly one of her kidnappers and has admitted being on the scene when she was killed. Yet Mr. Strickler's case was marred by government abuse that leaves his sentence tainted. The court, upholding that sentence, has sent a bad message to prosecutors and to judges reviewing habeas petitions.

The central witness against Mr. Strickler, Anne Stoltzfus, testified that she witnessed the abduction of Ms. Whitlock by Mr. Strickler and two accomplices. Her testimony painted Mr. Strickler as the leader and identified key details. It later emerged, however, that the prosecution had suppressed earlier statements and notes by Ms. Stoltzfus that would have undermined her testimony. A federal court found that this withholding violated the so-called Brady rule, which requires that prosecutors produce information that tends to undercut the government's case.

The Supreme Court, however, disagreed. Writing for a seven-member majority, Justice John Paul Stevens admitted that "there is a reasonable possibility that either a total, or just a substantial, discount of Stoltzfus' testimony might have produced a different result, either at the guilt or sentencing phase." But the court denied habeas relief because it found no reasonable probability that the evidence would have produced a different outcome.

This is, of course, inherently unknowable. When dealing with the death penalty, the distinction between possibility and probability only encourages judges considering habeas claims to act on their subjective sense of how a jury would likely behave. It also sends a signal to prosecutors that even certain willful suppressions of evidence will be treated as forgivable errors, not constitutional violations.

The better standard, as Justice David Souter pointed out in dissent, would have "the touchstone of the enquiry [be] whether the evidentiary suppression `undermines our confidence' that the factfinder would have reached the same result." Under that standard, Mr. Strickler at least deserves a new sentencing.