A senior Texas judge who refused to hear a last-minute appeal from a prisoner facing execution because her office "closed at five" was herself put on trial today in one of the most high-profile cases of alleged judicial misconduct in the state's history.

Sharon Keller, dubbed Sharon Killer by her detractors, was the subject of a hearing at the Texas commission on judicial conduct that could ultimately see her removed from the bench.

The case relates to her handling of the imminent execution of a convicted rapist and murderer, Michael Richard, on 25 September 2007. That morning the US supreme court had cast doubt on the constitutionality of using lethal injection - the form of death administered by Texas - by agreeing to rule on whether it amounted to cruel and unusual punishment.

Lawyers for Richard raced to file an appeal that would put a stay on his execution, which was due to take place that evening, but they were delayed by computer glitches.

They contacted Keller, who by then had gone home to deal with a worker doing repairs to her house. When, at 4.45pm, they requested a postponement of the execution, her reply was: "We close at five."

At 8.23pm Richard was put to death.

The apparently callous handling of the case led to a storm of protest and headlines around the world. Keller later claimed that she had been unaware of the lawyers' technical problems.

Keller faces charges including denying the rights of a condemned man. She is the highest-ranking judge to face misconduct proceedings.

A Republican, she has a reputation for her tough approach to justice in a state known already for its hard line on crime. In 1998 she ruled in a case involving a man with learning difficulties, denying him a retrial despite DNA evidence that appeared to prove his innocence.