I agree with Justice Aaron. The decision to admit the testimony of ICE Agent Andrew Flood was erroneous. But it was also likely harmless. Covarrubias was pretty clearly guilty of smuggling 193 pounds of marijuana across the border, as his story had a ton of holes and was not particularly credible. So letting Agent Flood testify about the structure of drug organizations etc. wasn't really the reason Covarrubias was convicted.
Justice Aaron discusses at length why Agent Flood's testimony should have been excluded, but doesn't really focus on the portion of that testimony that I find most problematic. Covarrubias claimed that he was a "blind mule" -- that he did not know the drugs were in his car -- and Agent Flood testified that blind mules are "fictional" and don't really exist. Stating that he had never come across anyone in his lengthy experience in law enforcement who was actually a blind mule, even though many of them claimed to be.
That seems obviously improper to me. Let's just change the facts slightly. How about this testimony: "I've been involved in law enforcement for many years. I've seen hundreds of defendants charged with murder. Lots of them say that they didn't do it. But that's simply untrue. I've never met someone who actually didn't do it. It's fictional. They're all guilty."