The Developers served evidence of fact from a single witness – the Fourth Defendant in the BTC Core Claim, Dr Pieter Wuille. He provided two witness statements. He discovered Bitcoin in around December 2010 and started contributing to the project in early 2011, joining the maintainer team for Bitcoin in late April 2011. He left the maintainer team in July 2022 but continues to be an active contributor to the Bitcoin project. Although he undertook his initial contributions to the project in his spare time, he said that since September 2014, contributing to Bitcoin has been part of his job, first for Blockstream and since 2020 for Chaincode Labs.

Having summarised his involvement, he went on in his first witness statement to discuss certain concepts related to Bitcoin and the Bitcoin Software. Some of these were used in a short but effective cross-examination conducted by Mr Gunning KC of Dr Wright and I discuss these points later. In the final paragraphs of his first witness statement, Dr Wuille refers to the first time he became aware of Dr Wright which was around the time Dr Wright posted a screenshot in a blog ‘that was supposed to be a message signed with one of Satoshi’s keys’. He continued:

‘I remember reading this blog post when it first came out, and reading articles responding to it which argued that it was not a genuine signature, and instead reused an existing, public signature by Satoshi from the bitcoin blockchain. I remember that I looked at the blog post and myself verified that it took an existing signature by Satoshi and converted it into OpenSSL format rather than the Bitcoin format so it didn’t look the same as the original. The most obvious tell is that the signature could not be identical to one that was already used. In short, the signature in the blog post proves nothing; I formed the view that it was a deliberate attempt at making an old signature look like it was a recent one.’

‘… I remember that when I reviewed the blog, it convinced me Craig Wright was not Satoshi…’

Dr Wuille’s short second witness statement was made in response to certain points made in Wright11. Those triggered certain recollections which Dr Wuille followed up by reviewing some contemporaneous records of particular developments in Bitcoin namely the introduction of the 520 byte limit on stack elements in the Bitcoin Source Code and the disabling of certain opcodes. Again, some of this material was used in the cross-examination of Dr Wright.

Overall, page for page, Dr Wuille’s first witness statement (dated 13 October 2023), as supplemented by his second (26 January 2024), turned out to be the most significant document in this Trial because his ability to detail when certain features of the Bitcoin system were introduced were used to devastating effect in cross-examination of Dr Wright, as I explain below. Each topic was explained in his witness statement clearly, so Dr Wright had more than fair warning of these topics. On some of them, Dr Wright’s prior deductions as to what happened turned out to be wrong. On other topics, unusually (bearing in mind that generally Dr Wright appeared very well prepared for cross-examination), Dr Wright was caught out. It does not matter why that was the case, but it may have been because Dr Wright had to concentrate so hard on keeping so many forgery plates spinning.

Counsel for the Developers offered to call Dr Wuille to address any questions I might have for him. Whilst it would, I am sure, have been interesting to discuss some of the technicalities with Dr Wuille, I decided it was not necessary to take up that invitation since none of his evidence was being challenged. Dr Wuille presented very clear and well-explained written evidence. Since, as I have said, none of it was challenged, I accept it in its entirety.