Did Donald Trump subvert the case against New York City terror suspect?

(CNN)President Donald Trump's Twitter declaration that the man charged with killing eight pedestrians and bikers in New York City "SHOULD GET THE DEATH PENALTY" has ignited controversy over whether Trump could have jeopardized the government's legal case.

Presidents have uttered vengeful statements in the wake of terror attacks and terrible murders before. Yet, as with all things Trump, his late-night missive went further and could cause greater trouble for prosecutors.
Still, with history as a guide and the present context of a defendant who apparently mowed down people in the name of ISIS, it is likely Trump's intemperate tweet has complicated -- but not wrecked -- the prosecution's ability to obtain the ultimate penalty.
    Judges bring extra scrutiny to capital cases, and federal prosecutors must show they are seeking the death penalty based on fair-minded, well-considered grounds distinct to an individual defendant. The rapid-fire (some might say knee-jerk) nature of a Twitter message by the person at the helm of the executive branch that includes the Justice Department, could undermine that deliberative process.
    "It is entirely inappropriate for the President to call for a specific punishment for a federal criminal defendant, especially one who has not been convicted," said Ron Weich, dean of the University of Baltimore law school and a former federal prosecutor.
    "It amounts to improper White House interference in Justice Department litigation. It pre-empts the careful deliberative process within DOJ about whether to seek the death penalty. It may taint the jury pool," Weich added.
    Joon Kim, acting US Attorney for the Southern District of New York, is overseeing the prosecution of Sayfullo Habibullaevic Saipov, a 29-year-old Uzbekistan native charged with two terrorism counts: providing material support to ISIS and violence and destruction of motor vehicles with willful disregard for human life.
    "At the end of the day," said Andrew McCarthy, a former federal prosecutor who writes for the National Review, "it makes Joon Kim's life more difficult. ... Any time a President spouts off about a legal case it's going to complicate work for prosecutors."
    Trump's statements, as they stand, likely would not be a factor not in jurors' consideration of Saipov's guilt or innocence, but rather in a sentence of, say life in prison or death. Even then, McCarthy added, jurors may not be influenced by Trump. They may be more inclined to recall the horrific events of that Halloween afternoon than anything the President asserted.
    In the past, pronouncements of presidents and other top officials in high profile legal case have prompted challenges, and eventually been rejected.
    Immediately after the 1995 Oklahoma City bombing, President Bill Clinton said, "These people are killers, and they must be treated like killers." He and Attorney General Janet Reno endorsed the imposition of the death penalty for the perpetrators, who were not yet caught. Lawyers for Timothy McVeigh, one of the bombers, later asked a judge to prevent Reno from not participating in the case. The move was rejected, and McVeigh was executed in 2001.
    Back in 1970, President Richard Nixon declared cult leader Charles Manson guilty before his trial was over. Amid an immediate debate over whether he had tainted the case, Nixon, a lawyer, withdrew his remark, reportedly saying, "the last thing I would do is prejudice the legal rights of any person, in any circumstances."
    The United States Constitution requires due process of law, including the presumption of innocence until a person is proven guilty.
    On Wednesday night, Trump tweeted: "NYC terrorist was happy as he asked to hang ISIS flag in his hospital room. He killed 8 people, badly injured 12. SHOULD GET DEATH PENALTY."
    He was back at it Thursday morning, tweeting: "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!"
    Trump's tweets and other remarks have continually become evidence in legal cases. Judges used his statements earlier this year to find that his first travel bans were wrongly directed at Muslims and religious rights.
    More recently, his campaign comments about US Army Sgt. Bowe Bergdahl were raised at a military trial. During the 2016 presidential campaign, Trump said Bergdahl "should be shot" for walking off his post. "In the good old days, he would have been executed."
    Bergdahl pleaded guilty to desertion and misbehavior before the enemy. A military judge said Trump's comments would not hurt Bergdahl's ability to receive a fair trial.
    "I am completely unaffected by any comments President Trump has made about Sergeant Bergdahl," Army Col. Jeffery Nance said, although he acknowledged Trump's statements during the campaign were "conclusory, condemning and damning of the accused."
    Asked by CNN's Sara Murray about Trump's comments regarding New York City, national security adviser H.R. McMaster said Thursday that the President has asked for "options" to assess how terrorism suspects should be held and tried.
    "What the President wants is to secure the American people from this threat and from mass murderers like this," McMaster said told reporters at the White House.
    He added that Trump has asked for options to assess if the US judicial system has "all the tools they need to combat this threat to the American people."
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