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Prosecutors secured a relatively rare federal hate crime conviction punishable by a tough sentence on Thursday as a Florida man pleaded guilty to leaving a voicemail that threatened to shoot people at a mosque.

Legal experts and Islamic advocates said it sends an important message at a time of tension for American Muslims.

Gerald Sloane Wallace, 35, admitted at a plea hearing that he made the threatening phone call to the Islamic Center of Greater Miami on Feb. 19, according to the Miami U.S Attorney's Office. He pleaded guilty to one count of obstructing the free exercise of religious beliefs, which carries a stiff 20-year maximum prison sentence, although he could get half that.

Prosecutors previously said Wallace admitted leaving similar threatening messages at other mosques. The charge was upgraded to a hate crime from a lesser offense punishable by up to five years in prison.

The Council on American-Islamic Relations estimates that hate crimes targeting Muslims increased 91 percent in the first half of 2017 compared with the same period last year. Federal data from past years suggests most hate crimes aren't reported, few are prosecuted, and only a fraction of these result in convictions.

"We welcome any kind of hate crime charge in a case like this when there's clearly an indication of victims being targeted because of their faith or ethnicity or national origin," said Ibrahim Hooper, a national spokesman for the advocacy group.

"If it is indeed an effort to show the Department of Justice will apply the law equally and will target those who attack the Muslim community, I think it's a good message to send at a time of rising Islamophobia," Hooper said.

Former federal prosecutor David S. Weinstein said the conviction sends a message that the Justice Department is taking such threats seriously. He notes that hate crimes are difficult to prove because they often turn on the strength of any evidence of a defendant's motivation.

"I think certainly in today's climate part of the reason people are charged is to send a message that we take this kind of conduct seriously. It's the deterrent effect that criminal prosecutions have," said Weinstein, who is now in private practice.

According to court documents, the message Wallace left at the mosque used profanity against Islam, the prophet Muhammad and the Quran and also made the shooting threats.

"l hate you Muslims, you Muslims are terrible. l hate you people. l'm gonna go down to your center, I'm gonna' shoot all ya'll," the message said, according to the documents.

Wallace's sentencing is set for Jan. 17 in Miami before U.S. District Judge Marcia Cooke.

His conviction comes as President Donald Trump's administration defends itself in court against accusations that it's unfairly singling out Muslims with its travel ban proposals. The administration, led by the Justice Department, has argued that these bans are aimed at protecting Americans from terrorism.

"The Justice Department will not tolerate threats of hate violence, which threaten whole communities' sense of safety and security," said John Gore, Acting Assistant Attorney General of the Civil Rights Division. "The Justice Department will continue to vigorously prosecute hate crimes so that all people, no matter how they worship, the color of their skin, or their country of origin, can live their lives freely and without fear."

Earlier this year, a Florida man was sentenced to 30 years in prison on state hate crime charges for setting fire to the Islamic Center of Fort Pierce, which had been attended by Pulse nightclub shooter Omar Mateen. No one was injured in that fire.

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