The use of general-purpose computers as touch-screen voting machines has created several difficult auditing problems. If voting machines are compromised by malware, they can adapt their behavior to evade testing and auditing, and paper trails are achieved through printing devices under the untrusted machine’s control. In this paper we outline and exhibit a prototype of a device that audits a voting machine through screen capture, sampling the HDMI signal passed from the computer to the display. This is achieved through a standard that requires a compliant voting machine to display signal markers on the summary pages before a vote is cast; compliance is enforced via alerts to the voter with a visual and audible signal while the screen is captured and archived. This direct feedback to the voter prevents a compromised machine from failing to invoke the device. We discuss the design and prototype of this system and possible avenues for attack on it.