Operation Roxburg, the multimillion-pound three-and-a-half-year police investigation into the Stepping Hill poisonings, was one of the biggest and most complex launched by Greater Manchester Police.
It involved 7,700 police 'actions', 659 witnesses, a 28,100-page prosecution file and 16,000 items of unused evidence material.
The arrest and charging of initial suspect nurse Rebecca Leighton in July 2011, until charges were dropped two months later, was thrown back in the face of the prosecution during the trial.
Chua's defence claimed the police had got it wrong then and were wrong now.
Outside court, Detective Superintendent Simon Barraclough said: "It's been a search for the truth and the jury has reached the right decision."