  We analyze the time pattern of the activity of a serial killer, who during
twelve years had murdered 53 people. The plot of the cumulative number of
murders as a function of time is of "Devil's staircase" type. The distribution
of the intervals between murders (step length) follows a power law with the
exponent of 1.4. We propose a model according to which the serial killer
commits murders when neuronal excitation in his brain exceeds certain
threshold. We model this neural activity as a branching process, which in turn
is approximated by a random walk. As the distribution of the random walk return
times is a power law with the exponent 1.5, the distribution of the
inter-murder intervals is thus explained. We illustrate analytical results by
numerical simulation. Time pattern activity data from two other serial killers
further substantiate our analysis.
