ALBANY — Defense attorneys on Wednesday began their effort to demolish the credibility of Todd Howe, a key prosecution witness in the federal corruption trial of Joe Percoco, former aide to Gov. Andrew Cuomo, and three businessmen who allegedly paid him more than $300,000 in bribes.In a Manhattan federal courtroom Wednesday, Percoco's attorney Barry Bohrer wasted no time in establishing Howe's years of lying to friends and employers, and living well beyond his ample financial means."Mr.