On a day of high drama at a specially-convened meeting of the International Tribunal in Paris investigating the three-day test held at Barcelona's Circuit de Catalunya after the Spanish GP, the FIA accused Mercedes of contravening Article 151c of the governing body's International Sporting Code.
The clause prohibits "any fraudulent conduct or any act prejudicial to the interests of any competition or to the interests of motorsport generally".
According to Mark Howard QC, representing the FIA, "undoubtedly Mercedes obtained information during this test and it is self-evidently prejudicial to the sporting competition".
At the heart of the team's defence is their longstanding argument that the test was hosted by Pirelli and, as such, they could not be held responsible for its staging or any alleged wrongdoing.
The team also seized upon the exact wording of Article 22.1, which both Mercedes and Pirelli were accused of breaking in their summons to attend the hearing.
It states that 'Track testing shall be considered any track running time not part of an Event undertaken by a competitor entered in the Championship, using cars which conform substantially with the current Formula One Technical Regulations in addition to those from the previous or subsequent year.'
"This was not a test undertaken by Mercedes. They are critical words in text of Article 22 - 'undertaken by'," argued Paul Harris QC, representing the Brackley-based outfit.
In a potentially-critical exchange that could be seen to provide Mercedes with an invaluable escape clause, it was also revealed that when Sebastian Barnard, the FIA's legal advisor, was asked by race director Charlie Whiting whether participation in the test could be considered to have been undertaken by Pirelli rather than a 'competitor', he replied: 'Yes, we could take this position, it is not an undertaking from the competitor'.
For their part, Pirelli begin their defence in the bluntest terms by stating that "we do not come under the jurisdiction or authority of the FIA". That announcement sparked a series of spikey exchanges as Howard dismissed Pirelli's testimony as "confused and missing the point", before thanking Ross Brawn for "giving the game away" with his admission that Mercedes would have gained "knowledge" through their participation.
In an unexpected twist, Mercedes also strived to turn the tables on Ferrari by accusing the Scuderia of breaching the rules surrounding in-season testing when they ran their 2011 car following the Bahrian GP.
The team did, however, offer an apology for instructing their two race drivers, Lewis Hamilton and Nico Rosberg, to wear unmarked helmets during the three-day event in order to ward off attention from any prying eyes.
Earlier, as the case for the prosecution was set out, it was announced:
- Although 'informal communications' took place between the FIA and Mercedes, the governing body did not receive an 'outlining' of when the test would happen or under what terms.
- Mercedes requested permission to stage the test in a telephone call with Charlie Whiting, the FIA race director.
- Upon receiving the request, Whiting took advice from the FIA's legal department who informed him the test would only be permissible if all the other teams were copied into the request and were provided with an equal opportunity to take part.
- The FIA have also maintained that although Pirelli's commercial agreement with the governing body permits up to 1000km of testing with any of the teams, their contract also stipulates they are bound to the FIA's own Sporting Regulations as well.
With Pirelli's testimony already delayed until the afternoon, a ruling on the saga is only expected to be published on Friday.
A guilty verdict against either party could have massive and far-reaching repercussions for the sport.
Pirelli remain F1's sole tyre supplier but are yet to sign a contract extension beyond his season while Mercedes' own future in the sport may be plunged into doubt if any punishment was considered too severe.