Mr Butt, who was 61, was found with serious injuries in his house in Hyrstlands Road at around 9pm on April 23.
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Police have released the picture of Mr Butt as they continue to appeal to the public for information.
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A 64-year-old man who was arrested as part of the investigation has been released from police custody.
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Detective Chief Inspector Tony Nicholson said: "I am hoping by releasing this image it may jog someones memory of when they last saw Mr Butt or if they saw him in the days before his death.
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"I would continue to ask people to come forward with any information they have to allow us to continue to piece together Mr Butts final movements before his death.