Image processing systems and methods are provided for authorizing the performance at a computer terminal of an age-restricted activity. An estimated human age is determined based on human characteristics of a structure detected in an image captured at the computer terminal. It is determined whether the structure exhibits at least one liveness characteristic indicating the human characteristics from which the estimated human age is determined have been captured directly from a living human at the computer terminal. A positive determination is made as to whether performance of the age-restricted activity is authorized if the estimated human age meets a predetermined age requirement and the structure is determined to exhibit at least one liveness characteristic, and a negative determination is made if: i) the estimated human age does not meet the predetermined age requirement; and/or ii) the structure is not determined to exhibit at least one liveness characteristic.