We employ an experimental research design to investigate patterns of breakdown of biometric identification machines in the December 2012 national elections in Ghana. Used on a national scale for the first time in these elections, equipment failures of the biometric machines were common. We identify a non-random pattern to machine breakdowns. Where domestic election observers were present, machines were less likely to break down. We also find that electoral fraud more commonly occurred in polling places where machines broke down. Our findings caution proponents of biometric identification machines that they do not necessarily provide impartial and uniform access to government services. Independent and non-partisan monitoring makes an important contribution to the proper functioning of such equipment.