Given that preserving human brains for more than a century is fairly uncommon, what do you think was the motivation for preserving Guiteau's brain?

One reason for preserving the brain may have been to study structural abnormalities that could have explained Guiteau's violent behavior. Alternatively, because Guiteau was well-known and infamous, his brain may have been preserved for use as a memento or as a warning to discourage presidential assassinations in the future.