The variable measurements were standardised so that they ranged from 1 to 0 and a preliminary calibration was undertaken using all 23 independent variables and a sample of. 67 cases. From this preliminary investigation five variables were omitted from the model since their coefficients did not have the expected sign (negative for mitigating factors and positive for aggravating factors), and thus lacked face validity. None of the coefficients for these five variables was significantly different from zero, even at the 80Vo confidence level.