  We propose a new method for the characterization of stellar stratification in
stellar systems. The method uses the mean-square radius (also called the
Spitzer radius) of the system as a diagnostic tool. An estimate of the
observable counterpart of this radius for stars of different magnitude ranges
is used as the effective radius of each stellar species in a star cluster. We
explore the dependence of these radii on magnitude as a possible indication of
stellar stratification. This method is the first of its kind to use a
dynamically stable radius, and though seemingly trivial it has never been
applied before. We test the proposed method using model star clusters, which
are constructed to be segregated on the basis of a Monte Carlo technique, and
on Hubble Space Telescope observations of mass-segregated star clusters in
order to explore the limitations of the method in relation to actual data. We
conclude that the method performs efficiently in the detection of stellar
stratification and its results do not depend on the data, provided that
incompleteness has been accurately measured and the contamination by the field
population has been thoroughly removed. Our diagnosis method is also
independent of any model or theoretical prediction, in contrast to the
`classical' methods used so far for the detection of mass segregation.
