Oil multinationals, Eni and Shell, will on Thursday be on the lookout as a Milan judge will decide for the first time whether $1.1 billion of the sum paid in the controversial Malabu oil deal was siphoned in bribes to win the license to the field.

Eni and Shell are embroiled in a long-running graft case over the purchase in 2011 of Nigeria’s OPL 245 for about $1.3 billion. The oil field is reputed to be one of Africa’s biggest oilfields. The controversial case involves Eni’s Chief Execuive Officer, Claudio Descalzi, and four former Shell managers including one-time Shell Foundation Chairman, Malcolm Brinded.

The Thursday ruling, involving Emeka Obi and Gianluca Di Nardo, is a case running parallel to the main trial of both oil giants. It may however give clues to what might be round the corner for the two companies.

Emeka Obi is one of the middle men who had claimed that he deserved a share of the $1.3 billion, saying he helped mediate negotiations between the oil giants and ex-Nigerian petroleum minister, Dan State.

Italian prosecutors allege that Mr Obi received a mandate from Mr Etete to find a buyer for OPL 245, collecting $114 million while Mr Di Nardo took $24 million of that amount for putting Mr Obi in touch with Eni.

Mr Obi, a Nigerian, and Mr Di Nardo, an Italian, are said to be middlemen.

Eni and Shell, as well as their managers, have denied any wrongdoing.

A legal source told Reuters on Tuesday that although the Thursday ruling will not tie the court’s hand in the main trial, it will nonetheless constitute a sort of pre-judgement.

“It’s clear the ruling will become a first building block in favour of the prosecution or the defence … it will be a first verdict by a third-party judge on the matter,” the source said Tuesday.

A fast-track procedure that began in November will ensure the judge be called on to decide whether Messrs Obi and Di Nardo should be convicted in the case or acquitted for receiving payments prosecutors alleged to be illegal kickbacks.

Messrs Obi and Di Nardo, who have previously denied any wrongdoing, asked for a fast-track trial which under Italian law allows any eventual sentence to be cut by a third. If found guilty, the individuals on trial face possible jail terms for bribery while the companies face hefty fines.

Earlier, some documents had been seized in a raid on a Swiss financier’s apartment that could be crucial to the case. The raid, according to Independent newspaper, uncovered a briefcase belonging to Mr Obi, who is in the dock along with several former Shell employees and current and former Eni executives.

According to Swiss prosecutors, the suitcase contained a laptop, two Nigerian passports, five sim cards and a hard drive containing 41,000 documents that prosecutors believe could be crucial to the trial playing out on the other side of the Alps.

Meanwhile, Italian prosecutors alleged that, of the total $1.3 billion fee paid by Shell and Eni for the oil field, $1.1 billion went not into the coffers of the Nigerian state but the accounts of former oil minister Dan Etete who then distributed hundreds of millions to well-connected individuals, including former president Goodluck Jonathan.

Mr Jonathan, who faces no charge on the case, has denied wrongdoing.

The busted Geneva apartment belonged to Olivier Couriol, a former Credit Suisse banker who has been named in two other international corruption cases. Mr Couriol, who is under investigation for his role in separate crime-related deals, said that Mr Obi was merely a friend who left the bag at his flat by mistake while on holiday. But a Geneva prosecutor, Claudio Mascotto, believes it was stashed there to keep it hidden from authorities.

Earlier in June, a court in Geneva said some of the documents found in Mr Couriol’s possession could be unsealed and be sent to Milan but Mr Obi launched another appeal, meaning a Swiss federal court must now decide on the matter. It is still unknown when the case will be dispensed with by the Swiss court but reports said authorities believe the documents may also contain details of other questionable deals in Nigeria’s oil fields.

TO READ MORE Click: Malabu Scandal: Shell, Eni await fate as Italian court rules on $1.1 billion ‘bribe’