  Decays of unstable heavy particles usually involve the coherent sum of
several amplitudes, like in a multiple slit experiment. Dedicated amplitude
analysis techniques have been widely used to resolve these amplitudes for
better understanding of the underlying dynamics. For special cases, where two
spin-1/2 particles and two (pseudo-)scalar particles are present in the
process, multiple equivalent solutions are found due to intrinsic symmetries in
the summed probability density function. In this paper, the problem of multiple
solutions is discussed and a scheme to overcome this problem is proposed by
fixing some free parameters. Toys are generated to validate the strategy. A new
approach to align helicities of initial- and final-state particles in different
decay chains is also introduced.
