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.
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.