A method for verifying a detection of a motion of a body using a passive infrared sensor, the method comprising: generating motion data (205a, 205c) based on a first signal received at a primary detection channel (103a, 103c; 203a, 203c) wherein the primary (103a, 103c; 203a, 203c) detection channel comprises a first pyroelectric detector, wherein the primary detection channel (103a, 103c; 203a, 203c), is configured to receive a first predetermined range of signals, including at least some infrared signals, wherein the first signal indicates a possible motion of a body; generating verification data based on a second signal, or absence of second signal, received at a secondary detection channel (103b; 203b) wherein the secondary detection channel (103b; 203b) comprises a second pyroelectric detector, wherein the secondary detection channel (103b; 203b) is configured to receive a second predetermined range of signals, excluding at least some infrared signals via an infrared blocker; wherein the primary (103a, 103c; 203a, 203c) and secondary detection channels (103b; 203b) are part of the passive infrared sensor; and verifying that the first signal indicates a motion of a body based on a comparison of the motion data with the verification data; characterised in that the verifying step comprises determining that the motion data (205a, 205c) and verification data have not been generated based on signals from the same source, as: if the motion data and verification data have not been generated based on signals from the same source it is concluded that the signal that generated the motion data is a detected motion, as it was blocked from reaching the secondary detection channel and so did not generate the verification data; and if the motion data and verification data have been generated based on signals from the same source then the signals cannot be that of a detected motion as it has passed through the infrared blocker and so it is not an infrared signal of a moving body. generating motion data (205a, 205c) based on a first signal received at a primary detection channel (103a, 103c; 203a, 203c) wherein the primary (103a, 103c; 203a, 203c) detection channel comprises a first pyroelectric detector, wherein the primary detection channel (103a, 103c; 203a, 203c), is configured to receive a first predetermined range of signals, including at least some infrared signals, wherein the first signal indicates a possible motion of a body; generating verification data based on a second signal, or absence of second signal, received at a secondary detection channel (103b; 203b) wherein the secondary detection channel (103b; 203b) comprises a second pyroelectric detector, wherein the secondary detection channel (103b; 203b) is configured to receive a second predetermined range of signals, excluding at least some infrared signals via an infrared blocker; wherein the primary (103a, 103c; 203a, 203c) and secondary detection channels (103b; 203b) are part of the passive infrared sensor; and verifying that the first signal indicates a motion of a body based on a comparison of the motion data with the verification data; characterised in that the verifying step comprises determining that the motion data (205a, 205c) and verification data have not been generated based on signals from the same source, as: if the motion data and verification data have not been generated based on signals from the same source it is concluded that the signal that generated the motion data is a detected motion, as it was blocked from reaching the secondary detection channel and so did not generate the verification data; and if the motion data and verification data have been generated based on signals from the same source then the signals cannot be that of a detected motion as it has passed through the infrared blocker and so it is not an infrared signal of a moving body. if the motion data and verification data have not been generated based on signals from the same source it is concluded that the signal that generated the motion data is a detected motion, as it was blocked from reaching the secondary detection channel and so did not generate the verification data; and if the motion data and verification data have been generated based on signals from the same source then the signals cannot be that of a detected motion as it has passed through the infrared blocker and so it is not an infrared signal of a moving body.