Auditing Elections Equipment In Maricopa County 

The Maricopa County Board of Supervisors voted unanimously on January 27, 2021 to authorize a forensic audit of ballot tabulation equipment used in the 2020 elections. The audit is the culmination of a year-long effort by Maricopa County to ensure the accuracy of the federally- and state-certified hardware and software used to count votes.

View the Maricopa County Technical Response Report (Jan. 5, 2021)
Learn More About the Vote >
Find 2020 Election Security & Accuracy Information>
View the 2020 Audit Timeline > 

Audit Overview  

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The multi-layered forensic audit is comprised of three separate audits performed by two United States Elections Assistance Commission Voting System Testing Laboratories and a Certified Public Accounting Firm.

The audit of the tabulation equipment’s software and hardware was performing by two independent Voting System Testing Laboratories: Pro V&V and SLI Compliance. The firms were hired to:

  • Analyze election equipment software and hardware’s hacking vulnerability
  • Verify that no malicious malware was installed
  • Test that tabulators were not sending or receiving information over the internet
  • Confirm that no vote switching occurred

As an added measure of transparency, the Board hired a reputable Certified Public Accounting firm, Berry Dunn, to review county contracts with Dominion Voting Services and verify that the county leased the tabulation equipment according to state and county procurement regulations. Read the report here.

Audit Results   

Maricopa County’s election equipment and software passed all tests performed by two independent firms hired to conduct the forensic audit, according to reports by two federally certified Voting System Testing Laboratories.

Read the Summary of the Audit Findings >
SLI Compliance Audit Report >
Pro V&V Audit Report >

1) Source Code Tests 


These tests were designed to verify if the same federally and state certified source code was installed on the equipment. Auditors conducted a full forensic clone of the drive which is a "bit-by-bit” copy. This allowed them to review deleted files, deleted file fragments, and hidden data that may be found in slack and unallocated space Source code extractions tested:

  • 20% of Election Day Tabulators (each firm tested 10%)  square check solid NO ISSUES 
  • 100% of Central Count Tabulators  square check solid NO ISSUES 
  • 100% of Election Management System work stations and servers
    square check solid NO ISSUES
  • 40% of Adjudication Stations (each firm tested 20%)  square check solid NO ISSUES


Pro V&V and SLI Compliance found that all software and equipment inspected was using certified software and was not modified.

2) Malicious Software and Hardware Tests


These tests looked for evidence of equipment tampering or software hacking. Auditors ran tests for viruses, malicious software, and foreign equipment or code that should not be installed on the tabulators or system on the following equipment:

  • 20% of Election Day Tabulators (each firm tested 10%)  square check solidNO ISSUES 
  • 100% of Central Count Tabulators  square check solid NO ISSUES 
  • 100% of Election Management System work stations and servers
    square check solidNO ISSUES 
  • 40% of Adjudication Stations (each firm tested 20%)  square check solid NO ISSUES 


Pro V&V and SLI Compliance found no instances of malicious software or hardware installed on the tabulators or system.

3) Network and Internet Connectivity Tests

Network-and-Connectivity-Tests2These tests looked for evidence of the tabulations system ability to connect to the internet and if the tabulators and/or system was transmitting information outside the closed air gapped system within the county tabulation center or while being delivered, returned, or used at a vote center.

  • SLI reviewed system registry, system files, installed programs, download history, audit logs, USB/Ethernet history logs.  square check solid NO ISSUES 
  • Pro V&V ran server commands to test for connectivity.  square check solid NO ISSUES 
  • Both firms physically inspected and traced the wiring of the air-gapped system between the server, tabulators, adjudication stations, and Election Management System workstations. square check solid NO ISSUES 


Pro V&V and SLI Compliance found no evidence of internet connectivity.

4) Accuracy Tests (Only in Pro V&V Scope of Work)

Tabulation-Accuracy2These tests checked that the tabulation equipment and software correctly captures, stores, consolidates, and reports the specific ballot selections, and absence of selections, for each ballot position.

  • Using test ballots from the November General Election, Pro V&V examined the accuracy of more than 1.5 million ballot positions.
    square check solid NO ISSUES 


Pro V&V found no evidence of vote switching and concluded that the equipment tabulated and adjudicated ballots accurately.

Myth Busters

  1. Were the auditors Certified?

Both Pro V&V and SLI Compliance are certified Voting System Test Laboratories and their certification is in good standing with the U.S. Elections Assistance Commission

The county sought out the best, most qualified firms to perform this audit. A certified Voting System Test Laboratory is the only firm with the combined skill sets and knowledge to identify vulnerabilities and to verify the systems are configured according to federal certification standards.

Using a Voting System Test Laboratory is essential, as the county asked auditors to review and analyze at the tabulation source code to perform a true assessment and identify vulnerabilities. Since the Department of Homeland Security designated tabulation equipment as critical Election Infrastructure, if the source code is exposed and posted online, that could jeopardize the integrity of voting systems across the country.

With four jurisdictional elections in 2021, including one on March 9, the county must also ensure its tabulation equipment remains certified.

  1. I’ve been hearing that this audit is not very thorough and would not find anything. Was this audit just surface level?
  1. Some people have said the auditors hired Dominion employees. Is that true?
  1. Why is it important that the software and hardware match what federal certification standards? What security tests were performed when the equipment was originally certified?
  1. Why did the County not audit the ballots?
  1. Why does the County provide a public wireless network? Does that expose risks to the tabulation equipment?

For more forensic audit photos, visit the Audit Timeline Multi-media Page.