GENEVA - International judges in the case of Kenyan Vice-President William Ruto have barred the use of recanted testimony.
The decision means prior recorded witness statements cannot be used by prosecutors at the International Criminal Court (ICC) in this case.
Key witnesses in the case changed their statements, which prosecutors said was due to intimidation and bribery.
Mr Ruto, who is being tried over unrest that followed 2007 elections, denies charges of crimes against humanity.
About 1,200 people were killed in the violence.
The latest ruling overturns a previous decision by judges to allow five of the witnesses' original statements to be included because they were convinced the witnesses had been interfered with.
Whichever way you look at it, this is a blow to the prosecution. It means they have lost evidence from five key witnesses.
However, the precise impact is hard to judge because so many of these hearings have been held in private session.
It partly depends on what else the prosecution has. If the prosecution doesn't have sufficient evidence this could go the same way as the case against President Uhuru Kenyatta and the charges may be thrown out of court.
The ICC is already considering a motion of no case to answer from Mr Ruto's lawyers.
That argument was heard in January and today's decision could have a bearing on it.