Kerik testified against two friends accused of lying to a grand jury when they denied paying for renovations at Kerik's apartments in Riverdale.
Prosecutors say in exchange, Kerik helped the brothers get a city contract.
Kerik said he could not recall details of the renovations.
The case against Frank and Peter DiTommaso dates to the 2006 grand jury investigation of Kerik, who's serving a 4-year term in federal prison.
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