THE AFL arranged for special testing of samples from Essendon players during 2012, months before the club's supplements scandal broke.

In a surprising twist, a video on YouTube has emerged featuring a speech from AFL medical officer Peter Harcourt last November at an anti-doping conference in Zurich.

Harcourt reveals the overseas testing and makes several strong comments about what Essendon's controversial 2012 supplements program involved.

The doctor also said he was setting up a program to monitor the players involved in the supplements regime because of fears they might contract cancer or have other hormonal problems.

The video emerged on the same day that Essendon, their suspended coach James Hird and ASADA returned to the Federal Court.

"We did have some wind of this (the supplements program) during the course of the year ... and so we did arrange through ASADA to have a number of specimens (from) these players sent to the Cologne laboratory, rather than the Sydney laboratory," Harcourt told the conference.

"But nothing came out of it."

Harcourt also explains why the AFL and ASADA teamed up for a joint investigation which could become a key piece of evidence in the Essendon-ASADA trial.

"The real reason was that under individual contracts all players are contracted to the League as opposed to the clubs," Harcourt said.

"A number of sports are like this and it was quite effective because it gave enormous power to ASADA to look at mobile phones, digital records, files and coerce interviews because it was allowed under the contract of the players to the League."

Hird's lawyer Nick Harrington raised the presentation during Wednesday's directions hearing at the Federal Court. Hird and Essendon are challenging whether ASADA acted outside its powers in conducting a joint investigation.

In the presentation, Harcourt admits to being shocked that no Essendon player "jacked up" or was moved to ask "what the hell was going on?" when asked to participate in the supplements program.

He said that the program was "a bit disturbing" and "highlighted the craziness or madness of certain individuals who were in the support staff who really didn't come to grips with what they were doing”.

Harcourt does not use any names of individuals who were at Essendon during that season in the presentation.

He also indicated the investigation had not, to that point, established exactly what had been administered to the players.

"There was probable use of performance enhancing drugs but without documentation and knowing precisely what was done we can't be 100 per cent certain, but there was clear risk of use," Harcourt said.

Harcourt suggested to the meeting that developers of the WADA code should consider whether violations could be applied if there was a risk of use.