Glendening, a Democrat who is barred from seeking a third term this November, issued a stay on the execution of Wesley Eugene Baker and said he would stay any other executions that come before him. Baker, 44, had been scheduled to die by injection sometime next week.
In announcing his decision, the governor repeated his support for the death penalty in especially heinous crimes, but said that "reasonable questions have been raised in Maryland and across the country about the application of the death penalty."
"It is imperative that I, as well as our citizens, have complete confidence that the legal process involved in capital cases is fair and impartial," the governor said.
Glendening had been under pressure to halt executions until he receives a study that is due to be completed in September by a researcher at the University of Maryland.
Baker is one of 13 men awaiting execution in Maryland, and critics say the death penalty is more likely to be imposed if the defendants are black and the victims are white. Nine of the 13, including Baker, are black, and many of the victims were white, including the woman Baker was convicted of killing.
Glendening said he would not lift the moratorium until the study is completed and reviewed by the state legislature. He said he expects the moratorium will remain in place for about a year, unless the next governor resumes executions after taking office in January.
Lt. Gov. Kathleen Kennedy Townsend, who also supports the death penalty in limited cases, had asked Glendening last week to impose the moratorium. She recently announced she is running to succeed him.
Illinois Gov. George Ryan declared the nation's first moratorium in 2000, citing the release of 13 death-row inmates whose convictions were flawed. Last month, a commission appointed by Ryan recommended reforms to reduce the possibility of wrongful convictions, including cutting the number of crimes eligible for the death penalty and videotaping police interrogations.
About 3,700 people are on death row for crimes committed in the 38 states that allow the death penalty.
Baker was sentenced to die by lethal injection for the 1991 murder of Jane Tyson, 49, who was shot in the parking lot of a Baltimore County shopping center, where she had taken her 4-year-old granddaughter and 6-year-old grandson shopping for tennis shoes.
Baker does not deny taking part in an attempted robbery when Tyson was killed, but his attorneys say there is not enough evidence to show he fired the gun. Gregory Lawrence, a co-defendant, was sentenced to life in prison.
Baker's lawyer, Gary Christopher, had filed two petitions with Glendening on Tuesday, one asking that his sentence be reduced to life in prison and one asking for a stay while the university study is completed.
Glendening has allowed two men to die by lethal injection, but commuted the sentence of a third, Eugene Colvin-el, to life without parole a week before his scheduled execution two years ago. Glendening said then that he was not absolutely certain that Colvin-el was guilty of the murder for which he was sentenced to death.
