Mircea Basescu, the president's younger brother, is accused of taking a USD 340,000 bribe to intercede on behalf of Sandu Anghel who was on trial for attempted murder.
According to anti-graft prosecutors, Mircea used his ties to the president to convince the mobster's son that he could get the charges dropped.
However, Sandu Anghel was ultimately sentenced to eight years and nine months in jail by the Supreme Court in May.
"I urge the policemen, prosecutors or judges who were in charge of this case to say if there was the slightest interference from me or on my behalf," said the president.
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"I am confident the judiciary will solve this case. If my brother violated the law, he will go before a court, just like any other citizen.
"I can assure you that between the need to strengthen the judiciary and the natural urge to defend my brother I will always choose the former."
A former prime minister and several ministers have been sentenced to prison for corruption, an unprecedented move in the former communist country.