New York (CNN) Lawyers for the alleged terrorist who killed eight people with a box truck in Manhattan last year say President Donald Trump's tweets calling for the death penalty and skewering Attorney General Jeff Sessions harms Sessions' ability to make an impartial decision on how to handle his case.

The attorneys for Sayfullo Saipov point to several tweets in the aftermath of the attack where Trump advocated for a quick execution. They also point to a recent tweet deriding Sessions for not thinking of the political implications for his decision to indict two Republican congressman.

They want the judge to either rule out the possibility of the death penalty or appoint an independent prosecutor in the case.

"The combination of President Trump's demand that the government Kill Mr. Saipov, his more recent tweets advocating that political calculations should inform Justice Department charging decisions, and his personal attorney's confirmation that Attorney General Sessions might be fired for not doing as the President wishes, make it impossible for Attorney General Sessions to fulfill his statutory duty to fairly and independently decide whether to seek the death penalty against Mr. Saipov," the public defenders, led by Jennifer Brown, wrote in a court filing.

Saipov, 29, has been charged with killing eight people and injuring a dozen others after he drove a pickup truck down a bicycle path near the World Trade Center on October 31. Saipov faces a 22-count indictment, which includes murder and terror-related charges. He has pleaded not guilty.

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