Border patrol agents watch the construction of prototypes of a proposed U.S.-Mexico border wall near Otay Mesa, Calif. (U.S. Customs and Border Protection handout/EPA-EFE/REX/Shutterstock)

The death of Kate Steinle on the waterfront in San Francisco in 2015 quickly became a national political touchstone. Steinle died after being struck by a bullet fired from a gun in the possession of Jose Ines Garcia Zarate, a Mexico native who was in the country illegally. The incident occurred on July 1, two weeks after Donald Trump announced his presidential candidacy by focusing on the danger posed by immigrants from Mexico so, in short order, Steinle became “beautiful Kate” in Trump’s campaign rhetoric, an immediate example of the threat posed by illegal immigration.

Last week, Zarate was acquitted of murder in Steinle’s death, a verdict that appeared to leverage doubt about Zarate’s intent when he picked up a firearm that he says he found shortly before the shooting occurred. To Trump and his supporters, though, the acquittal was proof that Trump’s call for a wall to prevent illegal entry was urgently needed. The refrain — often used by white nationalists — was for the building of “Kate’s Wall.”

This response is understandable, but it’s more complicated than it may seem. According to Immigration and Customs Enforcement records, Zarate may have illegally entered the country on at least three occasions — in February 1998, 2003 and 2009 — using established border checkpoints.

Since Trump began drawing new attention to the idea of building a wall along the border with Mexico, it has been pointed out that most of the contraband that enters the United States does so through those same border checkpoints. In 2015, the Drug Enforcement Administration wrote that Mexican cartels “transport the bulk of their drugs over the Southwest border through ports of entry (POEs) using passenger vehicles or tractor trailers,” as The Washington Post’s Christopher Ingraham reported in April. John Kelly, then the director of the Department of Homeland Security and now Trump’s chief of staff in the White House, acknowledged the same reality, telling senators during a hearing that illegal drugs “mostly come through the ports of entry.”

Of course, that’s drugs, which are a bit easier to smuggle into the country in a vehicle than a person. In 2006, the Pew Research Center assessed the modes of entry for those in the country illegally. Of the 11.5 million to 12 million people in the country illegally at that point, about 6 million to 7 million — 50 percent to 61 percent — entered the country by avoiding immigration inspectors. An additional 4 million to 5.5 million — a third to almost half — entered on a valid visa but didn’t leave. The rest entered on a border-crossing card, a document that allows Mexican nationals to cross the border without a visa.

How did Zarate enter? A representative from Immigration and Customs Enforcement confirmed to The Post that agency records first reported by the Los Angeles Times in 2015 were accurate. Zarate had entered the country on at least five occasions over the past 25 years. In 1993 or 1994, he entered and was eventually detained in Washington and deported. In 1996 or 1997, he entered the country again, with the same result.

Zarate’s three most recent entries were in 1998, 2003 and 2009. James Schwab, an ICE public affairs officer in San Francisco, acknowledged that the agency’s records matched what the Times reported: In 1998 and 2009, he was actually arrested trying to enter the United States at border crossings, the latter at Eagle Pass, Tex. In 2003, he reentered the country through a border crossing in Texas. After each of those crossings, he was imprisoned. It’s not clear whether he made it much farther into the country than the checkpoint.

Asked how ICE determines mode of entry for those it arrests, Schwab indicated that the information is often conveyed to the agency by the immigrant.

“It’s all self-reported,” he said. “We can’t really verify that information. … Oftentimes, we don’t know how or where the person came into the country.”

While Zarate probably entered the country through border crossings on more than one occasion, many of those immigrating illegally do not. When PolitiFact looked at the mode-of-entry question in 2015 (after it surfaced during the campaign), it spoke to Marc Rosenblum of the Migration Policy Institute. Rosenblum’s organization estimated that 17 percent of immigrants from Mexico in the country illegally arrived on a legitimate visa and then didn’t return when mandated — they overstayed their visas.

“Many, but not all, of the Mexican and Central American overstayers likely arrived legally by land,” Rosenblum told PolitiFact. He added that those who hadn’t arrived legally might have done so because they were “inadmissible, because they have committed serious crimes or are on a security watchlist.”

On Tuesday, the Department of Homeland Security (of which ICE and the Border Patrol are part) released data documenting a 24 percent drop in apprehensions along the border with Mexico. The drop yielded the lowest number of apprehensions since 1971, a function, the department wrote, of “the Administration’s commitment to enforce the rule of law as directed in the President’s executive order” of Jan. 25.

There has been a downward trend that predates Trump, however, as Customs and Border Protection data show.

From 2009 to 2014, the most recent year for which Pew has data, the number of unauthorized immigrants in the workforce has been largely flat. Even before that period, the population of immigrants in the country that increased the most significantly was people from Asia, not Mexico.

How Zarate got into the country most recently and ended up in San Francisco isn’t clear. ICE provided The Post with a statement about him.

“Mr. Garcia Zarate was removed from the U.S. on five occasions following unlawful entry,” the statement read, noting that he “was removed on the following dates: June 20, 1994; April 1, 1997; February 2, 1998; March 6, 2003; and June 29, 2009. ICE will continue efforts to take custody of Mr. Garcia Zarate and ultimately remove him from the country for the sixth time.”