The US Supreme Court in Nautilis, Inc. v. Biosig Instruments, Inc. held a patent is invalid for indefiniteness if its claims, read in light of the patent’s specification and prosecution history, fail to inform, with a reasonable certainty, those skilled in the art about the scope of the invention. The US Supreme Court rejected the Federal Circuit Court’s standard which provided for some ambiguity in the claim scope. The US Supreme Court can be found here Nautilis v Biosig