  We investigate properties of a classifier applied to the measurements of the
CP state of the Higgs boson in $H\rightarrow\tau\tau$ decays. The problem is
framed as binary classifier applied to individual instances. Then the prior
knowledge that the instances belong to the same class is used to define the
multi-instance classifier. Its final score is calculated as multiplication of
single instance scores for a given series of instances. In the paper we discuss
properties of such classifier, notably its dependence on the number of
instances in the series. This classifier exhibits very strong random dependence
on the number of epochs used for training and requires careful tuning of the
classification threshold. We derive formula for this optimal threshold.
