Trump has used the Halloween attack to push his agenda of tightening immigration laws and toughening anti-terror policies.
"NYC terrorist was happy as he asked to hang ISIS flag in his hospital room," Trump tweeted late Wednesday night. "He killed 8 people, badly injured 12. SHOULD GET DEATH PENALTY!"
He then resumed his call on Twitter Thursday morning.
"Would love to send the NYC terrorist to Guantanamo but statistically that process takes much longer than going through the Federal system. There is also something appropriate about keeping him in the home of the horrible crime he committed. Should move fast. DEATH PENALTY!"
Presidents typically don't comment on pending criminal cases because of the potential impact their statements can have. For instance, the defense could claim his comments will taint a jury pool.
The call for the death penalty was aimed at Sayfullo Habibullaevic Saipov, a 29-year-old Uzbekistan native who was living in New Jersey, is charged with providing material support to ISIS, violence and destruction of motor vehicles, said Joon H. Kim
, the acting US Attorney for the Southern District of New York. During the Halloween attack, he killed eight people by driving over them in a pickup truck. He did not enter a plea in federal court Wednesday.
"Mr. President, we all know he should get the death penalty," tweeted Andrew C. McCarthy, a former federal prosecutor. "But when *you* say it, it makes it harder for DOJ to make that happen."
"Trump helped the terrorist with this tweet. Now prosecutors will have to spend time dealing with motions that the jury pool is tainted," said Renato Mariotti, a former federal prosecutor.
Speaking to the press Wednesday, the President called the justice system "a laughingstock" and said he would consider sending the suspect to Guantanamo Bay.