Abstract: A method to label as defective a measure of an optical-trap force, that is exerted on a trapped particle located inside a living, dispersive, viscoelastic medium, including operations of: (i) determining a calibration constant between the optical trap forces and the sensed voltages; (ii) determining a first calibration function of the frequency of the particle oscillation with the active-passive procedure; (iii) computing a second calibration function of the frequency as the quotient between the calibration constant and the first calibration function; (iv) computing an energy function of the frequency as the product of the thermal energy of the trapped particle and the second calibration function; (v) checking whether the energy function converges to the thermal energy of the trapped particle as the frequency increases; (vi) if there is no such convergence, then label as defective the measure of the optical-trap force.