Experts skeptical of border wall effect
Several drug trade and policy experts told us a border wall likely would not have the impact Trump envisions.

"Traffickers have a variety of mechanisms at their disposal on how to overcome the wall," said Vanda Felbab-Brown, a senior fellow at the Brookings Institution.

Some of those tricks are outlined in a 2016 Drug Enforcement Administration report. Mexican Transnational Criminal Organizations "remain the greatest criminal drug threat to the United States," and their most common method of smuggling drugs remains vehicles legally coming through U.S. ports of entry. Illegal drugs are smuggled in concealed compartments in passenger vehicles or blended with legitimate goods in tractor trailers, the report said.

Smugglers also attempt to get drugs into the United States using catapults, drones, boats and tunnels. At least 225 tunnels were discovered on U.S. borders from 1990 to March 2016, according to the DEA.

"Traffickers have been very innovative in finding strategies to circumvent existing walls and border control thus far, and more of the same strategy (i.e. more of a wall) doesn't offer much promise as a successful strategy," said Rosalie Pacula, co-director of the RAND Drug Policy Research Center.

Illicit fentanyl, one of the main drivers of overdose deaths in the United States, mainly originates in China and comes in through the southwest border, Canada and U.S. postal service, experts said.

A commission established by an executive order from Trump lamented the ability of immigration officials and mail carriers to detect fentanyl, in part due to the small amount needed for psychoactivity.

"We are miserably losing this fight to prevent fentanyl from entering our country and killing our citizens," the commission reported. "We are losing this fight (predominantly) through China."

Key federal departments should coordinate to intercept illicit synthetic opioids delivered through mail and increase efforts to detect it using enhanced technology, additional manpower and canines, the commission recommended.

"Only a presidential directive will give this issue the top level attention it deserves from (the Justice Department, Department of Homeland Security and USPS)," the July report said.

The commission did not list a border wall in its recommendations for fighting the drug epidemic.