Lawyers for Boston Marathon bombing suspect Dzhokhar Tsarnaev asked a judge on Wednesday to declare the federal death penalty unconstitutional, citing recent bungled executions in Ohio and Oklahoma and arguing there’s mounting evidence innocent people have been executed.

In a flurry of pretrial motions, Tsarnaev’s lawyers said that the U.S. Constitution’s protection against cruel and unusual punishment prohibits the application of the death penalty because it’s not authorized under state law in Massachusetts. They cited “worldwide revulsion over the recurring spectacle of botched executions,” including one that left an Ohio inmate snorting and gasping during the 26 minutes it took him to die in January and another that left an Oklahoma inmate straining to lift his head off a pillow after supposedly being rendered unconscious last month.

Tsarnaev’s lawyers also asked the judge to bar federal prosecutors from arguing that targeting the crowded athletic event last year is a factor a jury should consider when weighing his possible punishment if he’s convicted.

The lawyers said the decision to bomb the marathon shouldn’t be an “aggravating factor” in determining whether he should receive the death penalty because prosecutors also argue he committed the offense after substantial planning to cause death and commit an act of terrorism.

“Stated differently, the allegation that Tsarnaev targeted the marathon is simply a more specific statement of the substantial planning allegation,” Tsarnaev’s lawyers wrote in a court filing.

Federal law requires the jury to reach its sentencing decision by weighing each aggravating factor cited by prosecutors against mitigating factors cited by the defense. Tsarnaev’s lawyers said having duplicative aggravating factors “can have no other effect than to introduce arbitrariness and unfairness into the jury’s sentencing deliberations.”

Last week, the defense asked a judge to eliminate another aggravating factor cited by prosecutors: Tsarnaev’s alleged betrayal of the United States. Tsarnaev’s lawyers said prosecutors, by citing his status as a newly naturalized U.S. citizen, are implying that he is “more deserving of the death penalty” than a native-born person who commits the same crime.

Tsarnaev, 20, has pleaded not guilty to several federal charges and awaits trial. Prosecutors allege he and his brother, Tamerlan Tsarnaev, planted two pressure cooker bombs near the marathon’s finish line, killing three people and injuring more than 260. Tamerlan Tsarnaev, 26, died following a shootout with police several days after the bombing.

Dzhokhar Tsarnaev’s lawyers acknowledge that a federal appeals court rejected a challenge to the federal death penalty in another Massachusetts case in 2007. But they asked the judge to eliminate the death penalty as a possible punishment if they are able to show that prosecutors gave erroneous instructions to the grand jury that indicted him.

The defense wants to see the legal instructions given to the grand jury. Specifically, the defense notes that the 30-count indictment includes 17 counts that carry the possibility of the death penalty and includes 26 special findings made up of factual allegations that must be established before a sentencing jury can consider imposing the death penalty.

Tsarnaev’s lawyers say the grand jury should have been informed of the significance of the special findings, “namely that by returning such findings, the grand jury was authorizing the government to seek the death penalty.”

(AP)