Definitions in arson law and relevant court decisions cover 'building' and 'motor vehicle.' After describing elements of the four degrees of arson in New York law, 12 problems of proof in arson prosecution are discussed. One problem is whether a warrant is required for search and seizure in the premises where the fire occurred and the absence of a provision for an administrative warrant in New York law. Another problem is the circumstantial nature of the proof of corpus delicti in arson cases, because the fire usually destroys all evidence of its incendiary origin. A problem in expert testimony in arson cases is the requirement that professional fire investigators may testify about the facts found in their investigation of the fire's origin, but they may not conclude whether the fire was accidental or willful. This is to be determined by the trier of fact. Regarding proof of defendant's guilt by circumstantial evidence, motive and consciousness of guilt are problematic issues. Other areas that hold problems of proof in arson prosecution are the testimony of accomplices and coconspirators, admission to private parties, character-witness testimony, the imposition of a fine, restitution, the use of a reckless endangerment charge, the use of insurance law to aid the prevention and investigation of arson, and prosecution for insurance fraud.