The claim that a wall would lead to a huge decrease in crime is not supported by statistics. Construction of a wall would not suddenly remove millions of undocumented immigrants already in the United States, and there is no evidence of a causal link between immigration and crime. As for drugs, 90 percent of heroin coming into the United States enters through the southern border. But it is mostly smuggled through legal ports of entry and not wall-less areas. Most Fentanyl arrives in the United States from China through the mail.

He exaggerated the numbers of border crossers and cited unverified tales of human trafficking.

Though border crossings have been declining for nearly two decades, Mr. Trump continued to stress the need for a border wall with exaggerated data and overstated claims.

“Last month was the third straight month in a row with 60,000 apprehensions on our southern border,” he said. “Think of that. We apprehended 60,000 people.”

That monthly figure for October and November — data for December was not yet publicly posted — includes the 51,000 people caught illegally crossing the border, as well as the 9,000 to 10,000 people who attempted to enter through legal ports of entry but were deemed “inadmissible” each month. In the 2018 fiscal year, apprehensions at the border averaged 33,000 per month.

And he recounted with graphic detail what happens to victims of smugglers: “Women are tied up. They’re bound. Duct tape put around their faces, around their mouths. In many cases, they can’t even breathe. They’re put in the backs of cars or vans or trucks. They don’t go through your port of entry. They make a right turn going very quickly.”

It is possible that Mr. Trump learned of a duct-taping case from law enforcement officers, but more than a dozen experts in human trafficking told The Washington Post and The Toronto Star that they had not witnessed or heard of such an episode.

For emphasis, he added, “It’s at the worst level — human trafficking — in the history of the world.” Millions of Africans were forcibly enslaved and trafficked during the 15th and 18th centuries.