A paedophile accused of killing two nine-year-old girls more than three decades ago has gone on trial for a second time as prosecutors seek to draw on scientific advances in forensics on top of evidence from an original trial.

Russell Bishop, who is accused of sexually assaulting and strangling Karen Hadaway and Nicola Fellows in October 1986, is being retried after his 1987 acquittal was quashed at the court of appeal in light of new evidence after advances in DNA testing. The girls’ families, including Karen’s mother, Michelle Hadaway, were in court for the start of the trial.

The case was never closed and has become the largest and longest-running inquiry in the history of Sussex police. Bishop, who is now 52 but was 20 at the time of the killings, denies murdering the children in woods about half a miles from Moulsecoomb, the area of Brighton where both girls lived.

A significant part of the investigation has involved re-evaluating scientific work performed for the 1987 trial using modern techniques. DNA profiling was available then but was in its infancy.

Facebook Twitter Pinterest Russell Bishop was acquitted at the original trial in 1987. Photograph: Sussex police/PA

Brian Altman QC, for the prosecution, told the court that the case against Bishop did not only rely on scientific evidence but its context within the story of the case as a whole, including the accused’s movements, his actions and “significant lies” he told police at the time.

Bishop returned to live in the Brighton area after his acquittal, but less than three years later, in February 1990, committed offences involving the attempted murder, kidnapping and indecent assault of a seven-year-old girl in the Whitehawk area of the city. She survived and identified Bishop as her attacker, the jury was told. This, with scientific and other evidence, led to his conviction in December 1990.

Altman said: “We say that the similarities between the events of which he was convicted in 1990 and those in 1986 are such that, together with all the other evidence in the case, they can lead you to the sure conclusion that the defendant was responsible also for the murders of Nicola and Karen a few years earlier.”

The jury, which will be taken to visit Moulsecoomb, were on Tuesday taken through the last known movements of the two girls using photographs from the time, maps and witness statements.

Altman told jurors they would be hearing from “a variety of people who witnessed tiny aspects of an otherwise uneventful Thursday evening in October 1986, who did not know then that they would be asked about it in a criminal proceedings then, let alone over 30 years later”.

Nicola and Karen were friends despite attending different schools and had gone out to play after school on 9 October 1986.

Their bodies were found the next day in dense woodland in the Wild Park area of the South Downs. The 2018 trial was told how Bishop had joined the search for the two girls, taking his dog and claiming it would be able to pick up the scent of one of the children from a discarded jacket.

This was all a pretence, said Altman, adding: “His effort was cynical and a deliberate attempt to divert attention away from himself. Knowing full well that it was only a matter of time before the girls would be found dead in the very area he was helping to search, this was his way of deceiving others into thinking he was not responsible.”

When the search was going on, Bishop also made a number of “pre-emptive, semi-confessional statements” at a time when only one person knew the girls were dead and that their bodies were lying in woods not very far away, said the prosecution.

At one stage, after telling a police officer that he was not searching anymore, he added: “If I found the girls and if they were done in I’d get the blame, I’d get nicked.”

The moment when the bodies were found in undergrowth was described to the jury.

Karen was said to have been lying across Nicola. A police constable who found the bodies had said both appeared to be sleeping and their hands were together. Altman said images of the girls as they were found showed that Bishop knew details only the killer could have known.

The jury were warned about the challenges of hearing evidence relating to events that took place more than 30 years ago and that the crime scene and surrounding areas had changed considerably since.

The trial continues.