Howman told New Zealand's LiveSport Radio on Friday that Armstrong's repeated claim he never has tested positive for a banned substance could no longer be regarded as proof of his innocence.

"What seems to have happened in this particular scenario is that it went on for many years under the noses of those who were supposed to be detecting it and at times probably with their knowledge," Howman told the New Zealand program from WADA's headquarters in Montreal.

Howman said Armstrong finally had been caught because fellow cyclists had broken a code of omerta (silence) and confessed their parts in a "conspiracy to defraud the sport."

He did not specifically identify the agencies or individuals he suspected may have turned a blind eye to doping by Armstrong or his teams. But he referred to "suggestions" contained in the report of the United States Anti-Doping Agency that irregularities in some Armstrong tests might not have been investigated as rigorously as they should have been.

Howman said failed doping drug tests were no longer the benchmark needed to identify cheats.

He used the case of Olympic track and field athlete Marion Jones to illustrate flaws in the system. Once considered the fastest woman in the world, Jones served prison time and gave back her five medals from the 2000 Sydney Olympics after being convicted of lying to federal investigators about using performance-enhancing drugs.

"Marion Jones didn't fail a test either and she competed for seven years, won all sorts of gold medals and world championships, was tested about 160 times and none of them was positive," he said.

"Lance Armstrong has (been) tested more than a couple of hundred times. None of them were positive in terms of recorded positives. There have been suggestions that there may have been a couple of them that were not fully investigated so they remain at the moment suggestions.

"What we have to say is the science can catch some but it doesn't catch them all. What we've been talking about over the last few years is that where there is evidence gathered in relation to cheating -- and it can be gathered by the police or by customs or by other people -- then it should also be brought together to sheet home a sanction process against the cheating athlete. That's what they've done in this case."

Howman said the result of USADA's investigation of Armstrong was a "compelling" case against the seven-time Tour de France winner.

"It's compelling, it's very thorough and you can't just sit back and say it's a collection of statements from liars," he said. "It just doesn't read like that.

"It reads like 10 years of systematic doping and that's been through the mill of sworn testimony, so if anyone is found out to have lied under oath, they can face charges of perjury -- and in the United States you can go to prison for that.

"This is compelling. This is a very compelling series of informants who have given evidence, trying to help their sport get clean and what they've done is broken the (code of silence) to do that and I suppose that's taken quite a bit of courage."

Howman said the USADA investigation had struck a significant blow against drug cheats in cycling, but "I think it will take a while to get rid of the culture that still pervades the whole sport."

"From our perspective, it's showing that cheats don't really prosper and we don't want them to," he said. "To support the clean athletes, you've got to make sure that those who have cheated for a while, when they are found out, are brought to heel."

Armstrong's decision not to defend or contest the charges made against him was surprising, Howman said.

"To be honest, I was surprised when he decided not to take part in the whole hearing process. There was his chance to tell everybody what the situation was, he would be able to cross-examine all of those who were giving evidence against him," Howman said. "I guess he decided on the advice of his lawyers not to partake and so it has led to this.

"It's a bit difficult now to see how he can sit on the sidelines and criticize it when he didn't even front up. That's not really the mark of the clean athlete."

Howman said WADA was now waiting to see whether cycling's governing body, the UCI, would support the sanctions against Armstrong recommended by USADA which could include a lifetime ban and the annulment of his seven Tour de France titles.

"The answer now is in the hands of the international cycling union because they have a right to appeal this and I'm sure they they'll look at it very carefully to decide whether they accept the jurisdiction of the U.S., whether they accept the process they've followed and whether they accept the results they've achieved," he said. "If they don't, then they'll appeal to the Court of Arbitration for Sport. If they elect not to do anything, then we (WADA) have got a right to appeal as well.

"We'll consider that in the same light. But at the end of that if nobody does anything the penalties remain, the sanctions remain and Armstrong remains the recipient of the report which shows him to be a cheat for all of his career."

In an earlier statement, WADA president John Fahey welcomed USADA's "reasoned decision" in the Armstrong case. But the statement said it would be inappropriate to comment further until the UCI had decided whether it would take the matter to appeal. It has 21 days to do so.