Newton hearings do not deal with mitigation, Lynnzer. They are held to establish the facts of the offence where the offence is admitted but the facts are in dispute, and where the facts would have a material effect on the sentence.
To stick to the offence of speeding, as it is the subject of dantray’s question, a Newton hearing would be necessary if a guilty plea was entered but:
(a) the prosecution alleges a speed of (say) 105mph in a 70mph zone (guideline sentence a fine of a week’s net income and either six points or 56 days disqualification)
(b) the driver maintains that the speed was 85mph (guideline sentence half a week’s net income and three points).
The Newton hearing would hear from the witnesses and the Magistrates would decide which version of events they prefer.
The “Alex Fergusson” defence mentioned is a submission made to suggest that “Special Reasons” existed so that the normal penalties should either be reduced or not imposed at all. My own view is that dantray’s wife is unlikely to succeed once with this argument, and certainly not twice.