The findings were announced in a statement released Wednesday by county officials. The independent review was conducted by IBM Security Services.
MORE: 118K Los Angeles County voters' names not listed on polling place rosters due to printing error
In the statement, county officials said that no voters were removed from voting rolls because of the roster error, and their right to vote was never at issue.
The Registrar-Recorder/County Clerk said the roster print problem ultimately affected approximately 12,000 voters who went to the polls and cast provisional ballots, which were processed immediately and counted as part of the official election results.
"What the report told us was that it was a software glitch," L.A. County Supervisor Janice Hahn said. "It's going to be updating our software and possibly giving the staff better training so they can recognize if something like this ever happens again."
The review verified that there was no pattern of voters being excluded from the printed roster due to demographic characteristics or geographic boundaries, officials said.
The county's voter information management system application had not been updated to process a format change, so the system generated voter records with empty spaces for the birthdates of 118,509 voters, the review found.
Since the birthdates were missing, the county's system incorrectly classified these voters as "underage" and left them off the printed precinct rosters, according to the county.
MORE: Los Angeles County launches independent review of error that left 118K voters' names off polling place rosters
The county's statement described the error with the following explanation:
"IBM ran multiple simulations to determine what happened. It found that the incompatible state database was initially used to develop a voter roster file for printing. That initial export was stopped after 118,509 records were processed with empty birthdate fields. Then a second export was started, using the County's own voter database. That export generated correct voter information. However, the system did not clear the erroneous data from the first export. As a result, the incorrect data was merged with correct data, leading to the error in printing the rosters."
The IBM review also investigated a 21-minute outage of the county's voter information website, LAVote.net, on the evening of the election after the polls had closed. The review found no evidence of a cyberattack and attributed the outage to heavy demand on the website.
IBM recommended that the county undertake the following corrective actions:
- Updating the software code so the state and local voter databases are compatible
- Implementing new quality control practices for Registrar-Recorder/County Clerk staff
- Resolving deficiencies in the system used to create the printed voter roster
- Increasing capacity and changing configurations on LAVote.net to accommodate periods of high demand
Registrar-Recorder/County Clerk Dean Logan said the county has already put in place measures to ensure that voter rosters are correctly printed for the General Election on Nov. 6, 2018.