A method of detecting living body contact at an electrical contact surface, wherein the living body has a detectable characteristic initial impedance and a corresponding characteristic time constant defined by the initial impedance upon touching the electrical contact surface when the electrical contact surface is at a touching voltage, wherein the characteristic initial impedance has a characteristic initial resistance ( R o) and a characteristic initial capacitance ( C 0) in series, and the time constant defines a time value which is equal to the characteristic initial resistance ( R o) times the characteristic initial capacitance ( C 0); wherein the method comprises: - sending a non-hazardous probing signal of less than 50 V to the contact surface, wherein the probing signal comprises one probing pulse or a plurality of probing pulses forming a probing pulse train, and the probing pulse has a base voltage level and a probing voltage level which is above the base voltage level and equal to the touching voltage or a probing voltage level which is below the base voltage level and equal to the touching voltage; - detecting an electrical response from the contact surface in response to the electrical probing signal, wherein the electrical response comprises electrical response signals; and - determining from the electrical response signals whether there is living body contact at the electrical contact surface; wherein the probing pulse rises from the base voltage level to the probing voltage level in a rise time which is shorter than the time constant to define a rising edge and stays in the probing voltage level for a duration longer than the time constant, or wherein the probing pulse has a base voltage level and a probing voltage level which is below the base voltage level and equal to the touching voltage, and wherein the probing pulse falls from the base voltage level to the probing voltage level in a fall time which is shorter than the time constant to define a falling edge and stays in the probing voltage level for a duration longer than the time constant; wherein the method comprises comparing the electrical response which is received in response to the probing signal in a time window which defines a detection time period with a reference response and determining whether the electrical response matches with the reference response to decide whether there is living body contact at the electrical contact surface; and wherein the reference response is an expected response resulting from application of the probing signal to the living body or to a passive electrical impedance network having the characteristic initial impedance of the living body, or wherein the reference response is an expected response determined with reference to a plurality of sample responses of a corresponding plurality of living bodies forming a sample pool, and the sample response is obtained by collection of response signals by application of the probing signal to a sample living body of the sample pool individually and each sample living body has a detectable characteristic initial impedance and a corresponding characteristic time constant defined by the initial impedance upon touching the electrical contact surface when the electrical contact surface is at the probing voltage; characterized in that, the reference response is a responsive current in the form of a current pulse having a current spike and a peak current magnitude ( I max), wherein the current pulse follows the probing pulse to rise instantaneously to a current peak in a rise time and which falls from the current peak to a non-zero steady state current in a fall time, the fall time of the responsive current being at least 10 times longer than the rise time of the responsive current. - sending a non-hazardous probing signal of less than 50 V to the contact surface, wherein the probing signal comprises one probing pulse or a plurality of probing pulses forming a probing pulse train, and the probing pulse has a base voltage level and a probing voltage level which is above the base voltage level and equal to the touching voltage or a probing voltage level which is below the base voltage level and equal to the touching voltage; - detecting an electrical response from the contact surface in response to the electrical probing signal, wherein the electrical response comprises electrical response signals; and - determining from the electrical response signals whether there is living body contact at the electrical contact surface;