DNA found in a farmer’s car after it had been set alight matched that of his estranged wife’s lover, a court heard.
The body of William Taylor, 69, was found in a river near Hitchin, Hertfordshire, in February, eight months after he was reported missing.
Angela Taylor, 53, and her partner Paul Cannon, 54, have denied murder and setting the farmer’s Land Rover on fire.
Gwyn Griffiths, a colleague of Mr Cannon, also denies murder.
All three have also pleaded not guilty to conspiracy to murder between 12 February and 5 June 2018.
Mrs Taylor, of Charlton Road, Charlton, is accused of encouraging Mr Cannon, of Pirton Road, Hitchin, to set light to Mr Taylor’s car on 26 May 2018 when it was parked outside his home in Harkness Hall, in Gosmore near Hitchin.
St Albans Crown Court heard a white towel doused with liquid was wrapped around the steering wheel and an end placed into a green petrol-type can.
DNA samples from a partially burned white towel and a blue and white checked shirt recovered from the scene matched that of Mr Cannon.
Eight days later, on 4 June, Mr Taylor was reported missing. His body was found on 10 February on a bank of the River Hiz, near Hitchin, two miles from Harkness Hall.
Forensic scientist Sarah Kalargeros told the jury DNA samples matching Gavin Foulds, Angela Taylor’s son from a previous relationship who lived with her, were also found on the towel and a grey and white pillowcase found in the car.
The prosecution had alleged this proved the garments used by the arsonist came from Mrs Taylor’s home.
Earlier, the jury heard Mr Taylor was “loathed” by Angela Taylor and Paul Cannon because he would not divorce her.
The trial continues.