Nigeria's court of appeal on Tuesday dismissed 15 charges against the Senate president related to an alleged false declaration of assets, but it upheld three other charges against him.
Bukola Saraki's three-year tenure as president of the upper house has been marred by numerous accusations of misconduct and investigations, though none have led to convictions.
The original charges are related to allegations that Saraki falsely declared his assets when he was a state governor from 2003 to 2011, to which he pleaded not guilty.
A Code of Conduct Tribunal cleared the Senate president of the charges in June, saying the case against him lacked substance.
The government mounted a legal challenge which led to Tuesday's ruling by the court of appeal that Saraki should be retried by the tribunal on three of the 18 charges against him.
The three counts relate to Saraki's acquisition of two houses in Ikoyi, an upmarket district in the southern commercial metropolis of Lagos.
"The appeal is dismissed in part in respects of the other 15 counts", said the judge, Tinuade Akomolafe-Wilson, at the appeal court in the capital Abuja.
The Senate president's camp has previously denied any wrongdoing and on Tuesday issued a statement in which it said Saraki had been "victorious" due to 15 charges being dropped.
Saraki ran unopposed for the post of Senate president, mainly with the backing of the opposition. He was not the ruling party's preferred candidate, which led to strains in his relationship with President Muhammadu Buhari.
The Senate president has been dogged by legal cases since taking office.
In October 2016 Saraki was cleared of altering Senate rules to get himself elected, and in March this year lawmakers cleared him of any wrongdoing over allegations that he attempted to evade payment of customs duties on a car.