The number of executions carried out by the US federal government since 1988 is set to double in May, with three lethal injections scheduled in a single week.
   
Convicted murderers Richard Tipton, Cory Johnson and James Roane are scheduled to die in the federal death chamber in Terre Haute, Indiana, on May 9, May 10 and May 12, respectively.
   
"They don't have much in the way of legal resources remaining other than a clemency petition to President George W Bush," said David Elliot of the National Coalition to Abolish the Death Penalty.
   
The three were members of an inner-city gang in Richmond, Virginia, sentenced to death in 1993 for taking part in a series of drug-related murders. All three are black.
   
In the US criminal justice system most crimes are prosecuted by states rather than the federal government. Last year, all 60 executions carried out were administered by states.
   
The federal death penalty was reinstated in November 1988 with the introduction of a law designed to combat drug trafficking known as the Drug Kingpin Act. Since then, Congress has added over 50 other crimes that qualify for death.
   
They include kidnapping resulting in death, murder for hire, fatal drive-by shootings, sexual abuse crimes resulting in death, fatal carjackings or aircraft hijackings and sending materials through the mail with the intent of killing.
   
Congress is currently discussing new additions that would expand the federal death penalty even further.
   
"There was a dramatic jump in the number of federal capital crimes in the 1990s as Congress expanded its jurisdiction over criminal acts that have traditionally been under the purview of the states," said Ginny Sloan of The Constitution Project based at Georgetown University's Public Policy Institute.
   
"It's also become a way for politicians to show voters they are 'tough on crime,'" she said.
   
The most notorious person put to death at Terre Haute was Timothy McVeigh, convicted of the 1995 Oklahoma City bombing which killed 168 people.
   
Since then, only two others have been executed for federal crimes and the last execution was in 2003. There are currently 41 people on federal death row, 24 of whom are black.
   
Moussaoui case
   
The government is seeking the death penalty for Zacarias Moussaoui, who has pleaded guilty to six counts of conspiracy in connection with the September 11 attacks on New York and Washington.
   
A jury in Alexandria, Virginia, will determine whether Moussaoui gets the death penalty or life imprisonment in a trial scheduled to begin next month.
   
In general, the number of executions in the United States has been falling in recent years, even while the federal death penalty expands in scope.
   
"The states are cutting back on their use of the death penalty, while the federal government is expanding," said Richard Dieter of the Death Penalty Information Center.

So far this year there have been two, with another scheduled Wednesday night in Texas. Marion Dudley faces execution for the 1992 shooting deaths of three people in a Houston drug house.
   
Critics argue that the federal death penalty is racially biased against minorities. If the three executions go forward in May, five of the six people put to death would have been either black or Hispanic.
   
A Department of Justice study released in 2000 found that 80% of the cases submitted by prosecutors for death penalty review were against minorities.