1. A method comprising: processing data in a first dataset that represents time-varying information about at least one pulse pressure wave propagating through blood in a subject acquired at a location of the subject; processing data in a second dataset that represents time-varying information about motion of the subject acquired at the location of the subject; and determining whether one or more segments of the datasets were captured from a subject other than an expected subject by analyzing morphological features of the segments, wherein the information about at least one pulse pressure wave propagating through blood in the subject comprises photoplethysmographic (PPG) data and the information about motion of the subject comprises one or both of motioncardiogram (MoCG) data and gross motion data.