  A search for physics beyond the standard model in events with at least three
leptons is presented. The data sample, corresponding to an integrated
luminosity of 19.5 inverse femtobarns of proton-proton collisions with
center-of-mass energy sqrt(s) = 8 TeV, was collected by the CMS experiment at
the LHC during 2012. The data are divided into exclusive categories based on
the number of leptons and their flavor, the presence or absence of an
opposite-sign, same-flavor lepton pair (OSSF), the invariant mass of the OSSF
pair, the presence or absence of a tagged bottom-quark jet, the number of
identified hadronically decaying tau leptons, and the magnitude of the missing
transverse energy and of the scalar sum of jet transverse momenta. The numbers
of observed events are found to be consistent with the expected numbers from
standard model processes, and limits are placed on new-physics scenarios that
yield multilepton final states. In particular, scenarios that predict Higgs
boson production in the context of supersymmetric decay chains are examined. We
also place a 95% confidence level upper limit of 1.3% on the branching fraction
for the decay of a top quark to a charm quark and a Higgs boson (t to c H),
which translates to a bound on the left- and right-handed top-charm
flavor-violating Higgs Yukawa couplings, lambda[H, tc] and lambda[H, ct],
respectively, of sqrt(abs(lambda[H, tc])^2 + abs(lambda[H, ct])^2) < 0.21.
