Neilson's trial commenced at Oxford Crown Court on 14 June 1976, amidst a media circus. He was charged with four murders, as well as various other charges of attempted murder, GBH, robbery, kidnapping and firearms possession. Prosecutors were unable to charge him with the murder of security guard, Gerald Smith, as he had survived more than a year and a day beyond the brutal attack, and the law prevented a murder charge being brought, despite his eventual death being a direct result of this attack. The law in the UK has since been changed to prevent this anomaly from recurring.
On 1 July 1976 Neilson was unanimously convicted on all charges, with the exception of two charges of attempted murder. He received five life sentences in total, with the judge insisting on a whole of life tariff, with no possibility of parole.