The detective who led the inquiry into an alleged race-fixing plot has denied trying to suppress comments from television pundit Jim McGrath.
Top jockey Fallon is among six accused of taking part in a race-fixing scam
At the Old Bailey, Acting Det Insp Mark Manning blamed a "misunderstanding" for not disclosing police notes of Mr McGrath's remarks to defence lawyers.
In a police interview, Mr McGrath had contradicted key prosecution witness Ray Murrihy's views, jurors heard.
Six men, including jockey Kieren Fallon, deny conspiracy charges.
Betting and form
The prosecution claims Mr Fallon and two other jockeys conspired to lose 27 specific races between 2002 and 2004 in order that a South Yorkshire businessman, Miles Rodgers, could make money by laying bets on the internet betting exchange Betfair.
Earlier in the trial, Mr Murrihy, the Australian racing steward and key prosecution witness, testified that in one of the races in question, Mr Fallon had eased down his horse in the final strides.
But the court heard that Mr McGrath, a Timeform analyst and regular on Channel 4's Morning Line racing programme, gave a different opinion about Mr Fallon's ride when he met four police officers investigating the 27 races.
The Old Bailey trial heard that police told Mr McGrath his statement would only be about betting and form.
Mr McGrath had expressed surprise that his views on the jockeys' performances were not disclosed to the defence.
Acting Detective Inspector Mark Manning was asked by George Carter-Stephenson, QC, for jockey Fergal Lynch, why Mr McGrath's notes were not put in evidence and disclosed to the defence.
Mr Manning said he had not asked for the notes which was an "oversight", but Mr McGrath had only been asked to give his opinion on his area of expertise.
Mr Manning added: "There was a misunderstanding about what Mr McGrath was being asked to do."
Six times champion jockey Fallon and five others, including Mr Lynch, deny plotting to allow 27 horses to lose so Miles Rodgers, a professional gambler, could win bets on races.
Jockeys Fallon, 42, formerly of Newmarket, Cambridgeshire, but now of Tipperary, Ireland; Lynch, 29, of Boroughbridge, North Yorkshire; and Darren Williams, 29, of Leyburn, North Yorkshire, deny the conspiracy between December 2002 and August 2004.
Rodgers, 38, of Silkstone, South Yorkshire; Lynch's brother, Shaun Lynch, 38, of Belfast; and barman Philip Sherkle, 42, of Tamworth, Staffordshire, also plead not guilty.
Rodgers also denies concealing the proceeds of crime. All the defendants are on bail.
The trial continues.