Despite border patrol ports of entry, x-ray technology, and machine guns, illegal drugs continue to enter the United States every day. Many of the drugs intercepted by the DEA cross at legal crossing points. Cocaine, heroin, and methamphetamines enjoy the highest demand in the United States. In fact, the demand is high precisely because they are illegal. These three substances' status as illegal drugs makes them more difficult to procure (i.e. lack of supply), which increases the demand. Their illegal status also contributes to them being subject to the black market's unchecked inflation as well as compromised quality. Fentanyl, for example, is a pain reliever that is often mixed with cocaine or heroin for its numbing effects. Fentanyl can be very dangerous when made illegally and is responsible for a number of deaths by overdose. The case of fentanyl is a perfect (and tragic) example of the consequences of lack of quality control in the black market.
As far as the means by which smugglers peddle their wares into the country, they use bricks, tires, and disguised containers to sneak drugs in—especially at legal crossing points. They also use tunnels (such as three recently discovered crossing the border into Arizona) and the US Postal Service. According to the Obama-era Office of National Drug Control Policy, most high-priced narcotics are taken through official ports of entry because the chances of success are better.
Given the fact that some estimates reveal that only 1% of illegally traded drugs are seized by authorities, many critical experts suspect that legalization and controlled prescription are a better way to tackle the persistent drug problem. In this way, the economic demand and drug-related deaths would likely decrease.