Many of the proposed solutions to the hierarchy and naturalness problems
postulate new `partner' fields to the standard model particles. Determining the
spins of these new particles will be critical in distinguishing among the
various possible SM extensions, yet proposed methods rely on the underlying
models. We propose a new model-independent method for spin measurements which
takes advantage of quantum interference among helicity states. We demonstrate
that this method will be able to discriminate scalar particles from higher spin
states at the ILC, and discuss application to higher spins and possible uses at
the LHC.Comment: 11 pages, 11 figure