Despite this, he refused, disliking the National Liberal policies and the extent to which they had aligned themselves with the Conservative Party. In 1930, Birkett was involved in the so-called Blazing Car murder case. On 6 November 1930, two men returning home in Northampton noticed a bright light in the distance and saw a man come out of a ditch at the side of the road, glance back toward the light and say "looks like somebody has had a bonfire". The two young men ran toward the light, saw it was a burning car and fetched a policeman. When the fires died away, a body was found inside the boot of a car with a face so charred it was impossible to determine the identity of the man; the numberplate of the car was intact, however, and traced to an Alfred Arthur Rouse. Rouse was arrested and appeared at Northampton Crown Court on 26 January 1931, charged with the murder of an unknown man. He was defended by Donald Finnemore, and the Crown was represented by Birkett and Richard Elwes. Rouse was damned by a series of events. When arrested, he made statements such as "I'm very glad it's over" and "I'm responsible" and that the car engine had been off at the time of the fire, ruling out the possibility of accidental ignition. When he appeared as a witness, the defendant claimed that after giving an unknown man a lift, he had found that he was running out of petrol and had asked the passenger to take the spare can in the car and fill up the fuel tank. While he was doing this, Rouse testified that he went to the side of the road to urinate, and while there heard a large explosion. He said he saw a large flame and became convinced the petrol tank would explode. As such he ran away as fast as possible, at which point he ran into the two young men on the road. The cross-examination of him and other witnesses by Birkett swayed the jury, and they took only fifteen minutes to find Rouse guilty of murder. After his appeal had been rejected by both the Court of Appeal and the Home Secretary, Rouse admitted that he had in fact committed the murder – although he never gave a reason – it was theorised that he had done so in an attempt to fake his own death. Despite his admission of guilt the identity of the victim has never been discovered. In 1934, Birkett acted as counsel for the second of the two Brighton trunk murders, a case which was described as "his greatest triumph in a capital case".