Dzhokhar Tsarnaev, pictured in a photo presented as evidence in the trial by the U.S. Attorney’s Office in Boston. (U.S. Attoney’s Office in Boston via Reuters)

The United States government sought and won a death sentence in the trial of Dzhokhar Tsarnaev for his role in the Boston Marathon bombing.

However, it is worth remembering something: The government cannot actually execute anyone right now. The Justice Department effectively has a moratorium on executions because it is reviewing the federal death penalty policy.

And even if the review immediately concluded that the federal protocol is fine as it stands, there is still the issue of the actual lethal injection drugs that would be needed for any execution. Federal officials say the Bureau of Prisons does not possess any doses of drugs intended for lethal injections because of this ongoing review, and these drugs are increasingly difficult for authorities to obtain.

[How a jury decided to sentence the Boston Marathon bomber to death]

“The Department of Justice has been conducting a review of the federal protocol used by the Bureau of Prisons, and has had a moratorium in place on federal executions in the meantime,” Patrick Rodenbush, a spokesman for the department, said in a statement.

Of course, there is likely a long appeals process ahead for Tsarnaev. His attorneys did not speak after he was sentenced, but they are expected to appeal the sentence; this process could be lengthy, which would delay the government actually confronting this issue in the case.

Federal death sentences are not frequently handed down, and inmates who arrive on death row often remain there for a while. There were 61 inmates on federal death row going into Tsarnaev’s sentencing, according to the Death Penalty Information Center. More than half of them were sentenced at least a decade ago, and 10 of them were sentenced before 2000.

[Parents of 8-year-old bombing victim asked government to drop the death penalty]

Still, this federal review points to larger issues facing the country’s capital punishment system in recent years. This review stems, in part, from an ongoing shortage of lethal injection drugs that has pushed the issue of capital punishment back into the news and back to the U.S. Supreme Court.

A federal jury sentenced Dzhokhar Tsarnaev to death for his role in the Boston Marathon bombings, rejecting arguments that he had fallen under his brother's influence and was remorseful. (Reuters)

A rare occurrence

It is rare for someone to receive a federal death sentence and even more unusual for that sentence to actually be carried out. Since the federal death penalty statute was reinstated in 1988 and expanded in 1994, three inmates have been put to death by the government, all of them were by lethal injection.

Even when the government does seek a death sentence, judges and juries rarely impose it, having opted for a life sentence in about two-thirds of these trials, according to the Federal Death Penalty Resource Counsel Project.

The three inmates who have been executed were all put to death more than a decade ago. Timothy McVeigh was executed in 2001 for the Oklahoma City bombing, while Juan Raul Garza was executed a little more than a week later for murdering three men.

[Full statement from Attorney General Loretta E. Lynch]

The last time that someone in federal custody was put to death was in 2003, according to Justice Department officials, when Louis Jones Jr. was executed. The Gulf War veteran was convicted for the 1995 kidnapping, rape and murder of an Army recruit, 19-year-old Tracie Joy McBride.

All three executions were carried out using three drugs that are listed in the execution protocol that the federal Bureau of Prisons has in place — the same protocol that is under review and cannot be used.

Under this protocol, condemned inmates must be brought into the execution chamber 30 minutes before the lethal injection is scheduled to begin. The protocol also calls for three sets of syringes containing the lethal drugs, one for the execution and another meant as a backup.

The first drug in the protocol, sodium thiopental, is meant to render the inmate unconscious. After that, pancurium bromide (a paralytic) and potassium chloride (which stops the heart) are supposed to be injected.

An ongoing drug shortage

This three-drug protocol resembles the same method used across the country until very recently, when an ongoing shortage of lethal injection drugs fractured the way executions are carried out in the United States. As the shortage has continued, states are scrambling to obtain the drugs needed to carry out executions.

“There’s no reason to believe that the federal government has better access to these drugs than any of the states do,” said Robert Dunham, executive director of the Death Penalty Information Center. “If the drugs aren’t available, the drugs aren’t available.”

States struggling to find execution drugs and have turned to new and untested drug combinations, resulting in some executions that seemingly went awry. One of the drugs the federal policy lists, sodium thiopental, was frequently used in executions across the country until the company that manufactured it stopped producing the drug due to its use in capital punishment; it was last utilized in an execution in Alabama in 2011, according to the Death Penalty Information Center.

A federal jury sentenced Dzhokhar Tsarnaev to death for his role in the Boston Marathon bombings, rejecting arguments that he had fallen under his brother's influence and was remorseful. (Reuters)

One of these problematic recent executions saw an inmate in Oklahoma writhe and grimace on the gurney during his lethal injection before dying 43 minutes after it began. President Obama called this execution “deeply troubling,” and he ordered then-Attorney General Eric H. Holder Jr. to review the death penalty.

Most executions are carried out with little notice, but cases like what happened in Oklahoma or an Arizona execution that lasted for nearly two hours drew increased media attention. The U.S. Supreme Court upheld the once-common three-drug combination in 2008, but they decided to take up lethal injection again this year amid a dramatically different landscape for capital punishment. (The arguments about whether Oklahoma’s execution protocols, which took place last month, wound up being unusually heated.)

Overall, a majority of Americans support the death penalty, though that number has been declining for two decades. Massachusetts, meanwhile, has not had the death penalty for more than three decades.

Holder said in February that he would support a national moratorium on lethal injections until the Supreme Court finishes reviewing lethal injection. He also said that the Justice Department has not yet completed the review of the death penalty that Obama ordered last spring.

Sari Horwitz contributed to this report