Single-trial classification of EEG data from Disorder of Consciousness patients (DoC) has proved particularly challenging. We present an approach that establishes a measure to relate the performance of single-trial classification of DoC patient EEG data with relational frequency bands and thus with their mental state. We evaluate our approach on 31 patient data sets from two studies, showing that our measure indicates for different data sets a particular likelihood for misclassifying either target or non-target class samples.