A methodology determining a response to exposure of a monitored person to a prohibited substance is provided. The methodology includes: first receiving movement data representing movement of the monitored person over time; second receiving an indication that a monitored person has been exposed to a quantity of a prohibited substance; first determining, from the received movement data, movement activity of the monitored person for a period of time before the exposure was detected; second determining a risk parameter based on at least (a) the amount of the quantity of the prohibited substance, and (b) the movement activity; issuing a notice to a supervising authority in substantially real time when the second determining results in a risk parameter that is above a first threshold; and issuing a notice to a supervising authority in non-real time when the second determining results in a risk parameter that is below the first threshold.