A trial of eight men accused of murder during the Birmingham riots almost collapsed when a judge declared a police officer had "invented a story".
Haroon Jahan, 20, Shazad Ali, 30, and Abdul Musavir, 31, died on 10 August after being hit by a car.
The eight defendants have been found not guilty at Birmingham Crown Court.
The jury heard Det Ch Insp Anthony Tagg had been found to have "invented" evidence given under oath during a hearing held in their absence.
The Independent Police Complaints Commission (IPCC) is investigating the officer's conduct.
The judge Mr Justice Flaux rejected an earlier application to dismiss the trial over the non-disclosure of evidence by the prosecution.
Defence counsel argued there could not be a fair trial because an offer of immunity to eye-witnesses was not revealed by the prosecution until the latter stages of the proceedings.
Mr Tagg had been judged to have lied on oath to the judge during a hearing held in their absence to establish why the issue of immunity was not disclosed, the jury was told.
In a submission to the judge, defence barrister Michael Turner said of Mr Tagg: "He came to court and on any view lied pretty extensively about what he had said to counsel."
Mr Justice Flaux told the court: "Mr Tagg realised he was seriously at fault for having failed to inform (prosecution counsel) and also for having failed to ensure that this material was disclosed to the defence.
"In effect he invented this story and then repeated that invention in the witness box."
The judge decided a fair trial could still take place, but said he found some of Det Ch Insp Tagg's evidence unreliable.
West Midlands Police said it had referred the matter to the IPCC, which confirmed it would be investigating.
Assistant Chief Constable Gary Cann said no officer involved in the case had been suspended during the investigation.
ACC Cann was asked at a press conference: "Is it correct that the judge found the senior investigating officer had lied under oath?"
He replied: "That was the finding the judge made."
He added: "My understanding is that it related to a very specific issue at a very specific time and didn't have a wider application around the integrity of the trial.
"Whatever the officers are alleged to have done, had it been so serious as to require the halt of the trial, then that's what the judge would have ordered and he specifically did not do that."