The Howland will forgery trial (Robinson v. Mandell) was a U.S. court case in 1868 where businesswoman Henrietta "Hetty" Howland Robinson, who would later become the richest woman in America, contested the validity of the will of her grandaunt, Sylvia Ann Howland. According to Howland's will, half of her $2 million estate () would go to various charities and entities, the rest would be in a trust for Robinson. Robinson challenged the will's validity by producing an earlier will that left the entire estate to Hetty, and which included a clause invalidating any subsequent wills. The case was ultimately decided against Robinson after the court ruled that the clause invalidating future wills and Sylvia's signature to it were forgeries. It is famous for the forensic use of mathematics by Benjamin Peirce as an expert witness. History Sylvia Ann Howland died in 1865, leaving roughly half her fortune of some 2 million dollars () to various legatees, with the residue to be held in trust for the benefit of Robinson, Howland's niece. The remaining principal was to be distributed to various beneficiaries on Robinson's death. Robinson produced an earlier will, leaving her the whole estate outright. To the will was attached a second and separate page, putatively seeking to invalidate any subsequent wills. Howland's executor, Thomas Mandell, rejected Robinson's claim, insisting that the second page was a forgery, and Robinson sued. In the ensuing case of Robinson v. Mandell, Charles Sanders Peirce testified that he had made pairwise comparisons of 42 examples of Howland's signature, overlaying them and counting the number of downstrokes that overlapped. Each signature featured 30 downstrokes and he concluded that, on average, 6 of the 30 overlapped, 1 in 5. Benjamin Peirce, Charles' father, showed that the number of overlapping downstrokes between two signatures also closely followed the binomial distribution, the expected distribution if each downstroke was an independent event. When the admittedly genuine signature on the first page of the contested will was compared with that on the second, all 30 downstrokes coincided, suggesting that the second signature was a tracing of the first. Benjamin Peirce then took the stand and asserted that, given the independence of each downstroke, the probability that all 30 downstrokes should coincide in two genuine signatures was . That is one in 2,666,000,000,000,000,000,000, in the order of magnitude of sextillions. He went on to observe: So vast improbability is practically an