Police arrested Evans after years of abductions and ransoms, but Nigerians are angered by media coverage of him.
Eighteen charges of non-declaration of assets against Saraki, the head of Nigeria's senate, were dismissed after almost two years of legal wrangling.
Nigeria's trade minister says the country could be a springboard for U.S. businesses in Africa, predicting good relations under President Trump.
The government is yet to secure a high-profile conviction for graft.
Officials have stolen $15 billion in federal defense funds, resulting in an army that is ill-equipped and unprepared.
He is Nigeria's second-highest Islamic authority and he denies misusing state funds on Rolls Royces and mobile phone bills.
An expert's view of the scale of corruption in Afghanistan and Nigeria, and their hopes for reform.
Much of Boko Haram's success has been down to the misappropriation of billions of dollars of Nigerian funds.
David Cameron referred to Nigeria and Afghanistan as "possibly the two most corrupt countries."
The country's non-existent workers have cost Nigeria $5 million so far.
Waripamowei Dudafa is alleged of involvement in a $2.1 billion arms scandal in Nigeria.
President Muhammadu Buhari has vowed to tackle "mind-boggling" levels of corruption in the oil industry.
Ex-Nigerian ruler Sani Abacha is suspected to have looted up to $5 billion in public funds during his reign.