Police investigating the murder of community support officer Julia James have appealed to a man in an image they released to come forward.
Ms James, 53, was found dead on 27 April near woodland in Snowdown, Kent, having suffered serious head injuries.
Kent Police said the man was seen in a "very relevant" location the following day, near to where her body was found.
Assistant chief constable Tom Richards said the man was the "key to unlocking what happened to Julia".
At a briefing in Folkestone on Friday afternoon, he told reporters the man was seen in the area police are focusing on, between Spinney Lane and Holt Street, near Aylesham.
He said: "I'm not saying here and now that he is a suspect, but he is of crucial importance to the investigation."
Mr Richards added: "Somebody knows who that man is and we desperately need you to make contact with us and help us identify who that person is.
"I need somebody to do the right thing, and give us the information we need to provide justice for Julia and her family."
Appealing directly to the individual he said: "If that person is watching please make contact with us."
A post-mortem examination found Ms James died from blunt force trauma and an inquest has been opened and adjourned.
Ms James had left her home in The Crescent to take her dog for a walk.
Police said on Thursday they were broadening the search area to include "a number of other locations" in addition to the woodland where her body was found.
Mr Richards said detectives were "still waiting for that critical phone call or piece of information" in the case.
Chief constable Alan Pughsley told BBC Radio Kent earlier that detectives still did not know what murder weapon was used, or the motive for the killing.
"Pretty much every chief constable in the land is offering whatever assistance they can to help find the murderer," he said.
"We have lots of lines of inquiries, lots to think about, and lots of work to do."
A £10,000 reward has been offered for information that leads to a conviction in the case.
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