It Doesn't Take a Thief: Optical-Scan Voting Systems Fail Even Without Adversaries

2026-07-29

AI Summary

This study addresses the reliability threats posed by non-malicious failures in optical scan voting systems, even in the absence of adversarial attacks. It presents the first comprehensive classification framework for non-adversarial failures, encompassing four key stages: ballot marking, scanning, tabulation, and verification. By integrating real-world case studies with an analysis of procedural, technological, and human factors within the election technology ecosystem, the work systematically identifies blind spots in current audit mechanisms. The research uncovers critical vulnerabilities undetectable by paper-based audits—such as incorrect ballot style distribution, misuse of ballot-marking devices, and poor ballot chain-of-custody practices—and delineates significant gaps in existing verification coverage. These findings provide empirical grounding and actionable directions for enhancing the robustness and trustworthiness of election systems.

Abstract

Optical-scan voting systems and their supporting ecosystem of people, processes, and technology are fallible. While a substantial body of work examines adversarial threats to such systems, we have encountered jurisdictions where the possibility of tabulator error is not fully internalized. Stakeholders there often find hypothetical attacks unconvincing, but some are persuaded by real-world accounts of equipment and procedural failures. This paper introduces a taxonomy of non-adversarial failure modes organized into intuitive categories: recording votes on paper, reading votes from the paper, combining votes as read into a reported outcome, and testing and verifying, all illustrated with documented incidents. We map common verification mechanisms against this taxonomy, identifying gaps that no paper-based audit can detect or correct, most notably failures that compromise the trustworthiness of the paper trail, such as giving voters the wrong ballot style (omitting contests they are eligible for, or including ones they are not), using ballot-marking devices to record votes, or failing to keep voted ballots secure and organized.

Problem

• optical-scan voting systems
• non-adversarial failures
• ballot errors
• paper trail trustworthiness
• tabulator error

Innovation

• optical-scan voting
• non-adversarial failures
• failure taxonomy
• paper trail integrity
• election auditing