U.S. Attorney General Jeff Sessions spent his brief trip to Portland smearing the city's good name.

On Sept. 19, the leading hard-liner of the White House's crackdown on immigrants and refugees arrived to decry so-called "sanctuary city" policies to an audience of federal prosecutors and immigration agents.

He reeled off a litany of violent crimes allegedly committed by undocumented immigrants, and urged Oregon and Portland officials to change their tune and cooperate with President Donald Trump's immigration crackdown.

His speech was filled with half-truths, misleading statistics and legally shaky arguments. Here are four of the biggest.

"After decreasing for over 20 years because of the hard but necessary work our country started in the 1980s, violent crime is back. The murder rate surged nearly 11 percent nationwide in 2015—the largest increase since 1968."

What Sessions gets right: The 2015 jump from 14,164 to 15,696 murders nationwide is the largest increase since 1968. But even with that one-year spike, the 2015 murder rate is still far below the highest point in recent history of 24,703 murders in 1991. As murder numbers get smaller and smaller, any increase looks larger when viewed as a percentage. America's murder rate is way down from the high point in the early 1990s, and one bump in 2015 doesn't show a reversal in crime trends.

"Between 2013 and 2015, [Portland] saw an increase in homicides of more than 140 percent."

Not only is Sessions' math wrong—the murder rate actually increased by about 112 percent between 2013 and 2015—but Portland's murder rate is also so low that any increase at all looks huge when expressed as a statistic. 2013 happened to be the year with the lowest murder rate in at least the past six years, with just 16 people killed. 2015 also happened to be the deadliest of those six years, but the city still saw only  34 murders.

"[Sanctuary] policies hinder the work of federal law enforcement; they're contrary to the rule of law, and they have serious consequences for the law-abiding residents of Oregon."

Sessions spent most of his remarks criticizing Portland and Oregon for refusing to comply with Immigration and Customs Enforcement detainers while emphasizing a commitment to the "rule of law." However, local law enforcement officials don't just ignore federal detainers and release undocumented arrestees out of the goodness of their hearts—they're following the letter of the law. In 2014, a U.S. District Court judge ruled that Clackamas County sheriff's deputies had violated a woman's constitutional rights by honoring a detainer request without any other reason to hold her. Since that ruling, any Oregon law enforcement agent who honors a request without any other legal authority to hold a person would be in violation of the Constitution and that court ruling.

"The vast majority of Americans oppose 'sanctuary' policies.  According to one poll, 80 percent of Americans believe that cities should turn over criminal aliens to immigration officials. A poll taken earlier this month of swing-state voters found the same thing: Seventy-seven percent support denying federal funds to sanctuary cities."

Sessions—and others in the Trump administration—have been touting this 80 percent figure for months. But many experts have questioned the legitimacy of the poll results—both because it is a notoriously unreliable type of poll called an "opt-in web panel sample" and because when it comes to asking about sanctuary cities, responses tend to shift dramatically based on the wording of the questions. Other polls on sanctuary cities show mixed opinions nationwide—but Portland doesn't reflect or respond to the opinions of people living in other states, it responds to the people who live here.