A smart watch worn by police community support officer Julia James in her final moments, captured a spike in her heart rate as she spotted her killer in woodland and tried to flee, a jury has heard.
The Apple watch belonging to Ms James showed that her heart rate had gone from 97 up to 145 within seconds at the point it is said she spotted Callum Wheeler in Ackholt Wood, Kent on April 27 last year.
Mrs James, 53, had been out walking her Jack Russell dog, Toby, when she was chased and hit over the head with a rail jack, jurors at Canterbury Crown Court were told.
Wheeler, 22, from Aylesham in Kent, admits killing her but denies murder.
Prosecutor Alison Morgan QC told the court that Mrs James had seen Wheeler around Ackholt Wood, near her home in the hamlet of Snowdown in Kent, in the months before she died, and described him to her husband Paul as “a really weird dude”.
On the day that she died, Mrs James saw Wheeler in the same place she had before.
Ms Morgan said: “The defendant was in that same place that Paul James and Julia James had seen him before, and it was at that point that Julia James’s heart rate surged.
“She took a sudden detour off the path that goes through the wooded area.
“She began to move along the edge of the field.”
The prosecutor went on: “She has run out of the wood, doubtless to try to escape her attacker, and has got as far as she could along the path.”
Mrs James then fell, either from a first blow to the head or by tripping, the court heard, and was subjected to a “violent and sustained blunt force trauma assault to the head”.
Ms Morgan said: “Given the serious nature of the violent injuries to her head which caused her skull to cave in, the majority of these injuries must have been inflicted when she was face down on the ground with her hood up.”
The court heard that she died “extremely rapidly” from the injuries.
The prosecution allege that Mrs James was killed with a metal railway jack which, they say, was later found in the defendant’s bedroom.
Ms Morgan went through forensic evidence found on the jack and Julia James’ clothing, including Wheeler’s DNA that was found on her boots, jacket and white vest that she was wearing underneath a jumper.
The prosecutor said that when officers went to arrest him at his home in Aylesham, he barricaded himself in his bedroom and made “clear denials”, but that he later made comments like “sometimes I do things I cannot control”.
She also told jurors that in the days before his arrest Wheeler walked around the local area with a bag believed to contain the alleged murder weapon, avoided police, and kept a check on a cordon around the scene of Ms James’ killing.
The jury was told that, while Wheeler denies murder, the prosecution claims that he intended to kill her or at least cause her really serious harm.
Ms Morgan told the court: “He waited for Julia James or another vulnerable female to be in those woods. Waited to ambush her. He chased her down.
“She ran, desperate to get away from her attacker. Unable to outrun him, caught by surprise wearing wellington boots, he struck her.
“She fell to the ground, she broke her wrist.
“Then, when she was face down on the ground, he struck her again and again. She had no chance of survival.
“When he hit her in that way repeatedly, using that weapon, he knew that and he intended it.”
Several members of Mrs James’s family attended court to hear the prosecution open the case.
The trial continues.