HUNTSVILLE, Texas (AP) - The state of Texas has executed a convicted killer whose lawyers say shouldn't have been eligible for the death penalty because of his low IQ.

Marvin Wilson was executed Tuesday evening at the state prison in Huntsville. The 54-year-old was condemned for killing a police informant two decades ago in Beaumont.

Wilson's attorneys had pointed to a psychological test that pegged his IQ at 61, below the generally accepted minimum competency standard of 70. They cited the U.S. Supreme Court ruling that banned capital punishment for the mentally impaired.

But lower courts agreed with state attorneys, who argued that Wilson's claim was based on a possibly faulty test and that his mental impairment claim wasn't supported by other tests.

The Supreme Court denied his request to stop the execution earlier Tuesday.