Because 4chan posts are anonymous, the researchers used a combination of indicators to identify Tarrant. 4chan’s “politically incorrect” board – known as /pol/ – provides the time, date and location of each post, allowing the researchers to match this against Tarrant’s travel to several countries over five years.

Tarrant also frequently provided personal information in his posts and he used the same distinctive language.

At times he repeated points he was known to have made elsewhere. He openly and proudly stated his Australian identity, even as he called for violence.

He also often made specific grammatical errors which make his posting stand out.

He uses this style in online writing samples as early as 2011, in his 2019 manifesto, and in a great deal of online posting in between.

Together, these indicators identify Tarrant.

The team of four researchers reviewed thousands of anonymous posts and hundreds of threads on /pol/.

They used the platform’s search function for particular words, phrases and images.

As a team, they carefully evaluated all the posts that included several of the above indicators.

They maintained a very high evidence threshold for including posts in their analysis.

They even excluded some important statements that were almost certainly written by him, but for which only one or two of the above indicators were present.

Their study was approved by the University of Auckland Human Participant Ethics Committee.

The authors of the report on which this article is based are Chris Wilson, co-founder and director of Hate & Extremism Insights Aotearoa (HEIA) and director, Master of Conflict and Terrorism Studies, University of Auckland (Waipapa Taumata Rau); Ethan Renner, Researcher, HEIA; Jack Smylie, Research Analyst, HEIA; and Michal Dziwulski, Researcher, HEIA.

A paper based on their study has been submitted for peer review and publication. More about the study will be released at heiaglobal.com

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