A teenager has denied creating a fake alibi knowing "perfectly well" he had just dragged PC Andrew Harper to his death.
Henry Long, 19 had been attempting to avoid arrest for stealing a quad bike in August last year when PC Harper got tangled in a tow rope attached to the car the teenager was driving.
Long drove for more than a mile along a country lane at speeds of some 42mph before PC Harper became dislodged, the Old Bailey has heard.
The 28-year-old died at the scene near the A4 in Berkshire.
Police arrested long within hours at the Four Houses Corner caravan site where the car, a Seat Toledo, has been located by a police helicopter.
Giving evidence, Long said he had no idea that the Thames Valley Police officer had been attached to his car.
He told jurors he felt "disgraceful", had sleepless nights and thought about the effect on Pc Harper's family.
But under cross-examination, Jonathan Laidlaw QC suggested Long knew how Pc Harper died and immediately set about making up a false alibi that he had been watching a Fast And Furious film with relatives at the travellers' site.
Long insisted he had made the decision to lie during his first police interview because he was "scared".
Long has admitted Pc Harper's manslaughter and conspiracy to steal a quad bike, but denies murder.
His passengers Jessie Cole and Albert Bowers, both 18, from near Reading, admit conspiracy to steal but deny murder.
The trial continues