A CCTV image showing a woman at a railway station three days before she was found murdered has been released.
Ms Birchwood had a shooting stick and was pulling a trolley
Sharon Birchwood's body was found at her home in Surrey on 7 December.
The 52-year-old had been dead for more than a day when her ex-husband made the discovery at the house in Ashtead. She had been bound with tape and cable.
CCTV showed her at Guildford station on 4 December. Police want to trace anyone who saw her or knew of her whereabouts in the days before she died.
Det Ch Insp Maria Woodall said Ms Birchwood went to Guildford library at about midday on 4 December.
The CCTV image from the town's railway station was taken later, at 1430 GMT, and shows what she was wearing that day, she added.
Stick and trolley
Police have also had a confirmed sighting of Ms Birchwood at Ashtead library at about 1700 GMT the same day.
The police inspector said: "We need to speak to anyone who saw Sharon travelling from Guildford to Ashtead, or from Ashtead to her home that day.
"We also need to hear from anyone who knows anything about Sharon's whereabouts between Tuesday at 1700 GMT and until the time she was found dead on Friday."
In the CCTV image, Ms Birchwood is seen carrying a shooting stick in one hand. She also had a bag on a trolley that she was pulling behind her.
Seen by the barrier on platform two, she was wearing a dark-coloured coat, white gloves and a white scarf.