This is just a quick pull from Tucson.com, but you can easily find the primary source material, which comes from CBP and the DEA, if you like:
“While Trump proposes building a wall to stop drugs from crossing the border and hiring thousands more Border Patrol agents, U.S. Customs and Border Protection statistics obtained by the Arizona Daily Star through a public-records request suggest the rhetoric coming from the White House reflects a misunderstanding of how and where hard drugs cross the border.
CBP statistics show 81 percent of the 265,500 pounds of hard drugs caught at the U.S.-Mexico border from fiscal year 2012 to fiscal year 2016 were stopped by customs officers at ports of entry, rather than by Border Patrol agents working in the desert and wilderness between ports.
Hard drugs normally are not driven on remote roads or hauled in backpacks through the desert, where they would be stopped by Border Patrol agents or come up against a border wall, although court records show agents catch hard drugs at highway checkpoints, such as the 5 pounds of heroin hidden in a man’s pants March 28 at the Interstate 19 checkpoint.
A far more common scenario in federal court cases in Tucson involves stashing hard drugs in vehicle dashboards or strapping them under clothes and trying to smuggle them through ports of entry staffed by customs officers.
Customs officers stopped 86 percent of the heroin caught borderwide from 2012 to 2016, CBP records show. Borderwide seizures of heroin by customs officers rose from 2,480 pounds in fiscal year 2012 to 3,280 pounds in fiscal year 2016, while Border Patrol seizures rose from 400 pounds to 560 pounds.“
Cocaine mostly comes in by air or sea. Opioids are more likely to come from Asia than transshipment through Mexico, and what does come through Mexico mostly comes through POE. Meth usually comes straight through POE. A border wall addresses none of this.