Ian Bailey faces legal costs estimated at between €2m and €5m, after the High Court awarded full costs against him for his long-running legal action against An Garda Síochána and the State.
Last March Mr Bailey lost his case, in which he sought damages for his treatment by gardaí during the investigation into the murder of Sophie Toscan Du Plantier in 1996.
The 64-day hearing was the longest civil case to run before a jury.
He had sued for wrongful arrest and several other related claims, but in a development at the end of the case most of his claims were struck out after the judge ruled he had not lodged his legal action within the six-year time limit required by law.
His lawyers had argued the State had wasted time and costs in the case by not making the strike-out application sooner.
However, today Mr Justice John Hedigan said the arguments from the plaintiff that 33.5 days of evidence were unnecessary was "unreal".
He said it was clear from the outset of the case the allegations made were so grave that the fullest possible ventilation was required in open court and before the jury.
The judge said he felt sure any application before the start of the case to determine the issue of the Statute of Limitations would have been resisted by the plaintiff who always wanted his case to be heard in court.
"There would also have been a public outcry that the defence would have been trying to close down the case on a technicality," the judge said.
He said a substantial number of people were entitled to their day in court and he would have approached any such application "with the firmest view that this case had to be heard in open court where a search light could be shined" on the allegations made.
He said the public interest deserved nothing less and that is exactly what happened and added it was incorrect to say most of the plaintiff's claim was withdrawn from the jury.
"The central plank or core of the case is what went to the jury for their decision”, the judge added.
He said it was unfortunate the case took so long, however, the breadth and depth of the case required all of the evidence.
Among the costs to be met by Mr Bailey are half the costs of travel expenses incurred by a juror, due to the case going on for longer than expected.
The judge agreed to a stay on the order for costs in the event of an appeal.
Bailey legal team argues against awarding of full costs
Earlier, lawyers for Mr Bailey had asked the court not to award full costs against him.
Mr Bailey's lawyers said the State's legal team wasted time and costs in the 64-day hearing by making a last-minute application to have most of the case struck out under the Statute of Limitations.
He had sued for wrongful arrest and several other related claims, but in a development at the end of the case most of his claims were dismissed after the judge ruled he had not lodged his legal action within the six-year time limit required by law.
However, a claim alleging conspiracy by some gardaí was allowed to go before the jury for determination. The jury found against him.
At the High Court this morning Senior Counsel Tom Creed said the defendants had wasted time and run up costs by not making an application under the Statute of Limitations until the very late stages of the case.
Mr Creed said of the 58 days of actual evidence heard in the case, they estimated that 33.5 of those days were unnecessary and not related to the issue that eventually went before the jury.
He said he was seeking costs for Mr Bailey for those days on the basis they had been wasted costs, because the application could have been made before the jury was sworn.
He also said Mr Bailey should be awarded costs for some of the pre-trial discovery proceedings.
However, Senior Counsel for the State Luán ó Braonáin said the burden was on Mr Bailey's side to avoid the ordinary rule that costs follow the event and the losing party pays the costs.
He said they had not established any special reason to avoid this rule other than a complaint that the application under the Statute of Limitations was made too late.
He said the Statute was pleaded at the outset of the defence and there was no reason for Mr Bailey's side to have been "shocked and dismayed", as they claimed they were when the application was made as they had known all along it was part of the defence.
Mr ó Braonáin said it was open to the plaintiff at all stages to ask for a ruling on this point but he chose not to do so.
He said the discretion of the court was not carte blanche or a blank page.
He said wholesale allegations of corruption, assault and conspiracy were made against An Garda Síochána and it was not only appropriate but in the public interest for the defendant to respond to those allegations to expose those concerned to the rigours of cross examination so they could be tested in front of the jury and the public.
He said it was the plaintiff himself who put the defendants in the position, compelling them to respond.
"Now having thrown the dice in relation to the making of those allegations he is saying I don't want to pay for taking the bet and that is not an appropriate way to deal with it", Mr ó Braonáin said.
He said from the defence legal team's analysis of the evidence, only one-and-a-half days of evidence might have been saved if their application had been made but he said this was part of the "cut and thrust" of litigation.
Mr ó Braonáin submitted a colour-coded chart of the evidence prepared by the defence, which he says outline the relevance and necessity of the witnesses.
He said there was no good reason to depart from the normal rules applying to costs.
Mr Justice John Hedigan is expected to rule on the matter later.