Forensic Disability Act 2011

For section 12(1)(a), a standardised measurement of intelligence must be used, if practicable, to assess a person’s general intellectual functioning.

If a standardised measurement of intelligence is used—

the person must be taken to have significant limitations in intellectual functioning if the measurement indicates that the person has an intelligence not higher than 2 standard deviations below the population average; and

the person must be taken not to have significant limitations in intellectual functioning if the measurement indicates that the person has an intelligence not lower than 2 standard deviations below the population average.

If the standardised measurement of intelligence is inconclusive as to whether or not the person has an intelligence higher or lower than 2 standard deviations below the population average, other indicators of general intellectual functioning may be taken into account in deciding whether or not the person has significant limitations in intellectual functioning.

In applying the standardised measurement of intelligence, the test result must be considered within the 95% confidence level as decided by the standard error of measurement of the test.