Abstract: Exemplary embodiments pertain to an automated sample processing system that includes a cassette having a superior component and an inferior component, where the superior component and the inferior component have a sufficient delta in opacity that is detectable by a sensor. An emitter is configured to emit a signal, where the signal passes laterally through one component of the cassette (or is diffused by it) and is configured to be received by a sensor. The sensor is configured to communicate the signal processing logic that is configured to interpret the signal and indicate the orientation of the cassette. Also disclosed is a method of detecting the orientation of a cassette in the automated sample processing system.