ASADA boss Ben McDevitt says the anti-doping body is still considering whether to appeal the not guilty findings for 34 past and present Essendon players.

ASADA has 21 days to decide whether to appeal after the players were cleared by the AFL anti-doping tribunal and McDevitt said on Wednesday it was a very real option.

McDevitt defended ASADA's handling of such a complex investigation and pointed out much of the delay involved in reaching the findings was due to the actions of others.

And he remained scathing in his criticism of Essendon's controversial supplements program in 2012 which involved "hundreds if not thousands" of injections to players.

"The absolutely deplorable and disgraceful lack of records of these injections means we still have young men not knowing what was injected into them," he said.

McDevitt said the penalties the AFL had previously imposed on Essendon over the matter had no bearing on ASADA's pending decision.

"I acknowledge the strong actions taken by the AFL in dealing with the governance issues.

"We have two sets of issues here, we have governance issues and we have anti-doping arrangements."

While the anti-doping body is "eagerly awaiting" a response from the Tribunal pertaining to former Essendon sports scientist Stephen Dank, McDevitt again encouraged Dank to come forward with any records from the club's supplements program.

But he said ASADA was not relying on evidence from Dank to push forward with an appeal.

"Stephen Dank has publicly stated that extensive records of the regime were kept," McDevitt said.

"But throughout this investigation, no such records have been found … I call once again upon Stephen Dank – if you've got records, produce them."

The ASADA chief executive said that Essendon's injection program meant the players had been used as 'pin cushions', and that allegations against the club had to be put to a tribunal for deliberations.

In almost an hour-long media conference in Canberra, McDevitt said he was optimistic heading into Tuesday's verdict that it would go in ASADA's favour.

"I was confident about the position we had with the players in terms of the quality of the evidence that was produced. I was confident that we would reach the level of comfortable satisfaction," he said. 

He followed the AFL and Essendon in suggesting that the anti-doping agency would review its processes, and that some of the country's frameworks were clunky and cumbersome. 

One hurdle that ASADA was unable to jump was its unsuccessful bid to compel witnesses Shane Charter and Nima Alavi to appear in front of the anti-doping tribunal.

But McDevitt said it was not a "fatal blow" for their chances in the verdict, which was reached after a hearing that stretched over two months.

"We all like to have credible witnesses who play a part in actually committing to the version of events, either on tape or a record of conversation and signing up to that and to maintaining that throughout the course of events. 

"We obviously haven't seen that in this case. I've never used the words 'star witness' (in reference to Charter and Alavi). I believe there was a very strong circumstantial case."