"It's a serious constitutional error, and I regret it's being pushed."

A capital punishment watchdog group claimed that the trial was "rife with serious constitutional errors: suppressed mitigating evidence, perjured testimony, and ineffective assistance of counsel."

Mr. Campbell filed one unsuccessful Federal court petition for a writ of habeas corpus, asserting constitutional errors in his trial.

Yet it was clear from the record of the case, he said, that no constitutional error had occurred in Mr. Thompson's conviction or sentence.

And he was denied an evidentiary hearing in Federal court despite claims of constitutional error and innocence.

Those cases hold, or clearly imply, that a conviction should not be reversed for constitutional error where the error did not affect the outcome of the prosecution".

Some precedents approving limits on civil liberties are now widely viewed to have been constitutional errors that would not be repeated today.

However, the courts relax their application of the plain-error test in cases involving constitutional error.

It was Judge Godbold's "horseback guess" that a third of all such cases suffered "constitutional error" sufficient for them to be overturned.

In death penalty cases, Federal judges find high rates of constitutional error.