Why do we write the name of Judges in a strange way?

I did a bit of law when I was in school, and recently, I recalled a unique feature of the law system regarding the way the names of judges were written, especially those with the title of Justice. Using an example:

Like other common law jurisdictions, when referred to in court judgments as Surname J. Judges in the New South Wales Court of Appeal are referred to as Justices of the Appeal (abbreviated Surname JA).

...(New Zealand) The "Mr" of the title "Mr Justice" was dropped on the appointment of Cartwright J to the High Court. In Court, all judges are addressed as "Your Honour", or "Sir/Madam".

So, if I was to write about a case, and the Judge had made a decision, and I wanted to relate that decision, I would write something like:

In view of the evidence and circumstances, it was ruled by Kritwal J. that there was not sufficient evidence to convict the accused, and hence, the accused was acquitted.

Why do the legal people do this? And what is the origin of this practice?

Solution 1:

It originated as a convenience for law reporters. The full title was (and is, in England) "The Honourable Mr Justice Kritwal", which is quite a lot to write, especially several times in a paragraph. So "Kritwal J" is a standard shorthand: in theory, it is pronounced "Mr Justice Kritwal".
The reversal is to avoid confusion: "J Kritwal" would normally mean John Kritwal, without reference to judicial status.

And there are abbreviations for other levels of judiciary : DJ Smith for District Judge, Smith LJ for Lord Justice Smith, and many others. wikipedia/Judicial_titles_in_England _and_Wales