  Many serial killers commit tens of murders. At the same time inter-murder
intervals can be decades long. This suggests that some serial killers can die
of an accident or a disease, having been never caught. We use the distribution
of the killers by the number of murders, the distribution of the length of
inter-murder intervals and USA life tables to estimate the number of the
uncaught killers. The result is that in 20th century there were about seven of
such killers. The most prolific of them likely committed over sixty murders.
