Briggen was born around 1850 and farmed at Sierra Morena in California, raising Berkshire hogs that won prizes at the state fair. He hired labourers from the poorest streets of San Francisco, men without families who would not be looked for, and brought them out to the ranch. They were not seen again.
He was arrested in 1902 after a farmhand named Steven Korad found finger bones in the hog pen and went to the authorities. Human remains were recovered from the property.
He was convicted, sentenced to life imprisonment, and died in San Quentin in 1903.
The figure of twelve or more comes from the number of men he was said to have hired over roughly two decades who could not afterwards be accounted for. There was no register of them, no identification of remains, and no charge beyond the case brought in 1902. The often repeated detail that he attributed the quality of his pigs to his feeding regime is from contemporary press writing.
The entry records the conviction and treats the twelve as an estimate of the missing rather than a count of the dead. What the case does illustrate is the selection: he chose men whose disappearance would produce no enquiry, which is the same mechanism that appears in this archive a century later.