Constantine was the head of DEA from March 1994 to July 1999. He was interviewed by NPR's John Burnett.

The intelligence was really a product of a transition in organized crime and drug trafficking in the United State. In beginning of 1990s, these powerful criminal organizations based in Mexico, primarily in Tijuana and Juarez, began to dominate the narcotics trafficking in the United States, and money laundering of billions of dollars out of US. As a result of this, more and more information would come in about the individuals running these drug mafias. As then as part of that, there were frequent allegations about Carlos Hank Rhon and the entire family, I believe, the sons and organizations and businesses.

Was it frequent intelligence, from dependable sources?

Most of the information was coming out of Mexico. It's always difficult to assess the reliability of sources of information when you're dealing in another country and you're not the primary law enforcement agency. But they were frequent and they were coming from different sources in different parts of the country. The corroboration of the information involving the allegations was difficult, and I suspect in many cases, almost impossible to prove or disprove.

Why impossible to prove or disprove?

If we had had similar allegations about a major business figure or public figure in US, probably investigative journalists, first, in my experience, then governmental employees at the prosecution level, and either in legislative hearings or actual investigations and grand juries, would eventually be able to determine the validity of that information, or if it was invalid. That was virtually impossible to accomplish in Mexico because law enforcement institutions and public institutions had been weakened and compromised so much as a result of the corruption of the drug traffickers, that there was not any strong system to be able to pursue those facts in Mexico.

So as a career law enforcement official with years of experience receiving intelligence, what was your gut reaction about what you were hearing about the Hank family?

I thought it cried out for an investigation to determine if the facts were true or not true. And I've always been someone who's had a career in this, and I like to deal in facts and evidence. Because our eventual goal, in any place I ever worked, is to arrest individuals or leadership of organizations and bring them to justice. And to do that you have to have facts and it has to be more than raw intelligence. But at the time I was there, as I said, that appeared to be virtually impossible to accomplish.

As far as you know, from when you were at DEA and since then, has there ever been a comprehensive investigation into the Hank family dealings?

To my knowledge, never in Mexico has there been a comprehensive investigation of the family, or the investigations that would be commensurate with what I would expect the standards in the United States. It would not be the type of investigation that really could be conducted in the United States about events that take place in another country. I think it would be inappropriate for us to do that. And secondly, it just wouldn't be feasible.

Why would an investigation of this type have to happen in Mexico?

All of the business records, the witnesses, the auditors, the bookkeepers, the bank managers, the narcotics traffickers, all of the people who could be potential witnesses for you are out of your control. And what we've seen in investigating organized crime in the US is that we pursue members somewhere in the business, and eventually information comes out that leads to very solid evidence for the principals of the organization. I was reading in this morning's paper about pursuing the big auction house, Sotheby's, in which the US attorney's office has secured cooperation of the key bookkeeper. That took months and months and I suspect significant pressure to be able to produce that information. All of those types of tools and levers are outside the control of the US.

Tell me about the nature of intelligence, its general reliability?

When intelligence comes in, frequently and substantially, and there's independent corroboration in which more than one person talks about the same event, it cries out for a major investigation to determine one way or the other whether its true or not. If such an investigation is conducted and it's rigorous, and it determines there is collusion and criminal activity, then there's a resolution to that. If it turns out that somebody has falsely been accused, it would seem to me they would relish having a major investigation so they can restore their credibility, and eliminate the allegations they say are raw intelligence. But this will only be solved through a very rigorous and objective investigation.

Was that kind of investigation against the Hank family proposed while you were head of DEA?

It was something that we could not do in the US. As I said before, in order to conduct this investigation, it would have to be conducted in country where that country lives and is the locus of all their employees and all of their financial enterprises. That was, for us, very difficult because at that period of time, there had been so many compromises of investigations of criminal activity even of lower level criminals. The premise that you could share confidential information that would deal with somebody of a level of a Carlos Hank Rhon and his public notoriety in that country, would have meant an immediate compromise of the information, and could get people hurt.