A jury trying Metropolitan Police Constable Alex MacFarlane, who admitted calling a black suspect a "n*****", has been discharged after failing to reach a verdict.
The defendant, a policeman for 18 years, was charged with causing racially aggravated intentional harassment, alarm or distress to Mauro Demetrio, 22.
Alex MacFarlane arriving at the court earlier on Thursday
The officer, 53, admitted telling Demetrio: "The problem with you is you will always be a n*****."
But he claimed it was not intended as racist abuse and he only used the term - which was recorded on the suspect's mobile - because Demetrio had done so first as he was taken into custody on suspicion of drink or drug-driving in east London on August 11 last year.
The jury of five men and seven women at Southwark Crown Court retired to consider its verdict yesterday.