David Smith (defendant) rented a flat in 1970. Smith’s brother lived with him in the flat, and they installed electric wiring, roofing material, asbestos wall panels, and floor boards in part of the flat. Those modifications were completed with the landlord’s permissions. In 1972, Smith gave notice that he was moving out. Smith asked the landlord to allow his brother to stay in the flat, but the landlord refused. Smith then removed the electrical wiring and damaged the roofing, wall panels, and floorboards in the process. Smith was indicted for damaging property belonging to another. During the trial, Smith presented evidence that he believed he was damaging his own property because he had installed the materials. The trial judge instructed the jury that the only defense under the statute charged was that the defendant had a lawful excuse to damage the property. The trial judge also told the jury that Smith’s belief that the property was his own was a mistake and was, therefore, not a lawful excuse. The trial judge then told the jury that they were bound to find Smith guilty. The jury convicted Smith, and he appealed.