  The possibility of strong biases in a multicomponent Maximum Likelihood fits
with component-dependent templates has been demonstrated in some toy problems.
We discuss here in detail a problem of practical interest, particle
identification based on time-of-flight or dE/dx information. We show that large
biases can occur in estimating particle fractions in a sample if differences
between the momentum spectra of particles are ignored, and we present a more
robust fit technique, allowing bias-free estimation even when the particle
spectra in the sample are unknown.
