Gov. Parris Glendening issued a stay on the execution of Wesley Eugene Baker, who was scheduled to die by injection sometime next week, and said he would stay any other executions that come before him. Only one other state that has capital punishment, Illinois, has imposed a similar moratorium.
Baker is one of 13 men - nine of them black - awaiting execution in Maryland.
Glendening, who supports the death penalty for especially heinous crimes, 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.
Glendening said he would not lift the moratorium until the study is completed and reviewed by the state legislature, which he estimated would be in about a year.
"I continue to believe that there are certain crimes that are so brutal and so vile that they call for society to impose the ultimate punishment," Glendening, a Democrat, said in issuing a stay of execution for convicted killer Wesley Eugene Baker, who was due to die by lethal injection next week.
"However, reasonable questions have been raised in Maryland and across the country about the application of the death penalty," the governor added.
Lt. Gov. Kathleen Kennedy Townsend, who also supports the death penalty in limited cases, asked Glendening last week to impose a moratorium until he receives the study the governor requested two years ago.
Townsend said at the time that it would be "tough to have a report come out and say this wasn't fair knowing that while the report was going on, that people were executed." She recently announced she is running to succeed Glendening, who cannot seek a third term.
Illinois Gov. George Ryan declared the nation's first moratorium in 2000. Last month, a commission appointed by Ryan recommended 85 reforms to reduce the possibility of wrongful convictions. Some of the reforms included cutting the number of crimes eligible for the death penalty and videotaping police interrogations.
This is another in a recent series of concrete signals - from judges and lawyers and politicians and even from the Supreme Court itself - that there is growing concern over whether the death penalty is being imposed fairly and accurately and without racial bias, reports CBSNews.com Legal Analyst Andrew Cohen.
He "wouldn't be surprised if the leaders of additional states in the near future decide that it is safer and even perhaps more cost efficient to evaluate death penalty procedures to find out whether they need to be fixed or scrapped," Cohen said.
Baker was sentenced to die by lethal injection for the 1991 murder of Jane Tyson, 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 being present when Tyson was killed, but his attorneys say there is not enough evidence to show he fired the gun.