Nuhu Ribadu brought more than 1,000 cases to court as head of the EFCC
Authorities in Nigeria have dropped charges against the former head of the country's anti-corruption agency.
Nuhu Ribadu had been accused of not declaring his assets while in office.
He was named head of the Economic and Financial Crimes Commission (EFCC) by ex-President Olusegun Obasanjo, but was removed when he stood down in 2007.
Mr Ribadu told the BBC from the United States - where he has been living in voluntary exile - that he was delighted "justice had been done".
"I'm happy, I'm pleased. I'm an innocent person who has been persecuted for such a long period of time," he told the BBC's Focus on Africa programme.
Correspondents say there is speculation that Mr Ribadu will be appointed a special adviser on fighting corruption to Acting President Goodluck Jonathan.
Mr Ribadu's lawyer, Femi Falana, told the BBC his client now had many options.
"Wherever Ribadu is, you can be sure he is going to contribute his quota towards fighting corruption," he said.
'Change of direction'
Mr Ribadu brought more than 1,000 cases to court as head of the EFCC.
Before his appointment no company in Nigeria had ever been charged with bribery.
His critics accused him of pursuing cases only against enemies of Mr Obasanjo and leaving his friends untouched.
But Mr Ribadu said the people who had brought the case against him had been abusing government institutions to persecute him and stop him doing his job.
"These guys were desperate to destroy everything that was done on the ground, and they started with me.
"They wanted to kill me and I left the country," he said.
Mr Jonathan was named acting leader in February because of the continuing illness of President Umaru Yar'Adua, who has not been seen in public since November 2009.
Mr Ribadu was sacked shortly after Mr Yar'Adua won elections in 2007.
He said the changes at the top had probably helped his case.
"Luckily we have a new government that is refusing to go in the direction of the former leadership - or the leadership that is not in office now," he said.
"They decided to do what is right, and therefore just withdrew the charges against me."