The hearings, billed as the most significant in the history of CAS, are due to begin at 9am local time tomorrow and continue until either Friday or Saturday (January 26 or 27).

It is hoped that a decision will be announced at some stage between January 29 and February 2.

The closed hearings, taking place in the International Conference Centre of Geneva rather than the CAS headquarters in Lausanne due to the sheer numbers of people attending, have been split into two groups.

Christophe Vedder has been named the President of both groups and will be joined in each by fellow German, Dirk-Reiner Martens.

Hamid Gharavi of France will also sit on the panel for the first group, which has 28 athletes, while Austria's Michael Geistlinger will play a similar role in the second group of 11 Russians. 

Grigory Rodchenkov, the former Moscow Laboratory director and the main witness in allegations against the athletes, and Richard McLaren, head of a World Anti-Doping Agency-commissioned investigation, are expected to testify via video or telephone link.

All of the 39 are accused by the International Olympic Committee (IOC) of involvement and complicity in a scheme in which urine samples were illegally tampered with and replaced with fake, clean samples during Sochi 2014. 

A key part of the Russian defence is expected to involve attempting to disprove the testimony provided by Rodchenkov, the mastermind behind the scheme before fleeing Russia for United States and becoming a whistleblower.

He currently remains in the US and is part of the witness protection programme. 

Around 10 to 12 of the case rest entirely on his testimony, which includes a "Duchess List" of athletes supposedly taking banned steroids, insidethegames understands, rather than on any scientific evidence.

Others are implicated by IOC-commissioned analysis of test tubes from Sochi 2014, which showed scratches indicative of tampering, as well as DNA results and analysis of salt levels in samples.

The IOC has said that it fully backs Rodchenkov's credibility as a witness.

A Russian Investigative Committee supposedly conducting its own probe has claimed to have found evidence disproving the IOC cases.

They claim to have obtained documents relating to the doping samples of 15 of the Russian athletes implicated claiming that they were transported in daytime and legitimately registered rather than transferred in a clandestine nighttime operation, as Rodchenkov and others allege.

Another key question to be ruled upon concerns the IOC attempt to award life bans to those who dope at a Games and therefore violate the Olympic Charter.

If successful, this could set a key legal precedent.

Cases involving biathletes Olga Zaytseva, Olga Vilukhina and Yana Romanova have been suspended and will not be heard this week.

Bobsleigh's Maxim Belugin is the one Russian athlete not to have appealed following his disqualification.

He is believed to have produced a positive test result following reanalysis of his samples, although full details of his case have not been disclosed.