A Texas judge in the county that sends more inmates to death row than any other in America defended a ruling in which he said capital punishment was unconstitutional.

Saying he could assume that innocent people had been executed, state district judge Kevin Fine ruled in a pre-trial motion in a capital murder case this weekend that the death penalty was unconstitutional.

He found himself facing a torrent of criticism from high-profile Texans including state governor Rick Perry, who described the ruling as a "violation of public trust".

Fine, a Democrat who is heavily tattooed and says he is a recovering alcoholic and former cocaine user, answered some of the criticism during a court hearing yesterday.

"To say that I am ignoring precedent or legislating from the bench I think is slightly overreaching," he said.

He said there was no precedent to guide him in resolving the issues raised by defence lawyers in a case involving a man accused of shooting dead a Houston woman and wounding her sister during a robbery in front of their home in June 2008.

Lawyers for John Green argued that Texas' death penalty statute was unconstitutional because it violated their client's right to due process of law under the Fifth Amendment.