Ecclestone, who could also be jailed if found guilty of bribing a public official, got a boost this week when a witness - who like Gribkowsky worked on the F1 account for public bank BayernLB - testified in Munich.
Initially, Briton Ecclestone was seen shaking his head when the witness agreed with suggestions the F1 chief executive wanted to "get rid of" BayernLB as a shareholder of the sport.
"From my point of view, our departure was in his interest," the former bank employee said, according to Austria's Kleine Zeitung newspaper.
"Banks as shareholders were not wanted, in his view," the witness explained. "I'm quite sure he wanted us to sell."
The witness revealed they became less and less involved in the F1 account as Gribkowsky and Ecclestone worked more closely together.
"It (the witness' involvement) became less and less and eventually it stopped altogether," the witness said.
The prosecutors claim that others were excluded from Ecclestone and Gribkowsky's talks due to the negotiations about the controversial $44m payment.
But Ecclestone claims he only paid up after Gribkowsky threatened to divulge false information about his family's tax affairs to the British authorities.
The witness on Tuesday supported Ecclestone's version.
The former BayernLB employee recalled a letter, containing claims that Ecclestone was still in charge of the Bambino family trust, that Gribkowsky once placed on Ecclestone's desk.
The witness said that when Gribkowsky was rebuked for leaving the letter for Ecclestone, "He (Gribkowsky) just laughed".
However, it is reported that the very same witness also testified in Gribkowsky's trial, and the very same judge ultimately issued a guilty verdict.
Kleine Zeitung said three more BayernLB-connected witnesses will testify on Wednesday.