A crash which claimed the life of a 32-year-old woman was caused by vandalism to one of the tyres on her car, police said.
Detectives are now treating the death of pharmacist Joanna Smith as manslaughter after forensic tests showed a tyre on her Honda Jazz had been punctured deliberately.
Mrs Smith, from Northampton, is thought to have been unaware of the vandalism when she set off for work in Irchester on the morning of April 10.
The victim, originally from Poznan in Poland, was pronounced dead on the eastbound A45 near Earls Barton after the damaged tyre caused her to crash while travelling at between 60mph and 70mph.
Detective Chief Inspector Martin Kinchin, from the East Midlands special operations unit major crime team, said: "While investigating the incident that led to Joanna's death, our collision investigation team established that it was likely that tyre failure caused a loss of control of the car."
Following the collision, officers were informed by members of the public that a further three vehicles parked in close proximity to the Honda had also sustained tyre damage at the same time.
The victim's vehicle was parked in a communal car park near her home in Grange Park when the tyre - which only partially deflated - was punctured.
Mr Kinchin added: "We believe that someone deliberately damaged the tyre on Joanna's car which ultimately resulted in her death.
"We do not believe Joanna was specifically targeted but was the tragic victim of senseless vandalism."
Anyone with information about the deliberate damage of tyres in the Grange Park area over the Easter Bank Holiday is urged to contact Crimestoppers anonymously on 0800 555 111 or the Operation Houston investigation team on 101.