  If mutual gravitational scattering among exoplanets occurs, then it may
produce unique orbital properties. For example, two-planet systems that lie
near the boundary between circulation and libration of their periapses could
result if planet-planet scattering ejected a former third planet quickly,
leaving one planet on an eccentric orbit and the other on a circular orbit. We
first improve upon previous work that examined the apsidal behavior of known
multiplanet systems by doubling the sample size and including observational
uncertainties. This analysis recovers previous results that demonstrated that
many systems lay on the apsidal boundary between libration and circulation. We
then performed over 12,000 three-dimensional N-body simulations of hypothetical
three-body systems that are unstable, but stabilize to two-body systems after
an ejection. Using these synthetic two-planet systems, we test the
planet-planet scattering hypothesis by comparing their apsidal behavior, over a
range of viewing angles, to that of the observed systems and find that they are
statistically consistent regardless of the multiplicity of the observed
systems. Finally, we combine our results with previous studies to show that,
from the sampled cases, the most likely planetary mass function prior to
planet-planet scattering follows a power law with index -1.1. We find that this
pre-scattering mass function predicts a mutual inclination frequency
distribution that follows an exponential function with an index between -0.06
and -0.1.
