Blood found on a plastic duct in a derelict property belonged to Damien Holmes, Bingley Magistrates were told.
Holmes, 19, of Mannville Grove, Keighley, pleaded guilty to burglary with intent to steal at Wharfedale House, Keighley.
Prosecutor Raj Kumar said police found metal shuttering had been forced open and a boiler removed from the property.
But forensic investigations also discovered blood on a plastic duct, which was identified as belonging to Holmes.
The magistrates on Tuesday adjourned the case for a pre-sentence report to be completed.
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