  Tracking of gamma-ray interactions in germanium detectors can allow
reconstruction of the photon paths, and is useful for many applications.
Scrutiny of the kinematics and geometry of gamma rays which are Compton
scattered only once prior to full absorption reveals that there are cases where
even perfect spatial and energy resolution cannot resolve the true interaction
sequence and consequently gamma-ray tracks cannot be reconstructed. The photon
energy range where this ambiguity exists is from 255 keV to around 700 keV.
This is a region of importance for nuclear structure research where two-point
interactions are probable.
