  Aimed at progress in mega-electron volt (MeV) gamma-ray astronomy, which has
not yet been well-explored, Compton telescope missions with a variety of
detector concepts have been proposed so far. One of the key techniques for
these future missions is an event reconstruction algorithm that is able to
determine the scattering orders of multiple Compton scattering events and to
identify events in which gamma rays escape from the detectors before they
deposit all of their energies. We revisit previous event reconstruction methods
and propose a modified algorithm based on a probabilistic method. First, we
present a general formalism of the probabilistic model of Compton scattering
describing physical interactions inside the detector and measurement processes.
Then, we also introduce several approximations in the calculation of the
probability functions for efficient computation. For validation, the developed
algorithm has been applied to simulation data of a Compton telescope using a
liquid argon time projection chamber, which is a new type of Compton telescope
proposed for the GRAMS project. We have confirmed that it works successfully
for up to 8-hit events, including correction of incoming gamma-ray energies for
escape events. The proposed algorithm can be used for next-generation MeV
gamma-ray missions featured by large-volume detectors, e.g., GRAMS.
