Although in the course of a conversation the interchanging of these terms might be acceptable, they actually require separate definitions when applied to legal matters. A legal system is designed to redress problems or issues which are a threat to society or its occupants. It is only natural, therefore, that the legal system should reflect the wishes of its subjects.
Fairness refers to legitimate and unbiased conduct in the course of making a decision or controlling an activity, equality refers to the absence of bias or discrimination in approach and/or outcome (where the former is often held to be paramount) and justice, the most often coined of terms, is something else entirely. Corrective justice is designed to compensate for a wrong or irregularity and distributive justice to the attempt to ensure that all receive equal treatment. Ideal justice (or, simply, a perfect solution) is the ultimate goal of most legal systems (which are in turn dictated by the morals and tenets of the society in question) although reality often insists that we must reconcile ourselves to attainable justice (the most expedient solution) as individual cases require individual responses. Values are principles or attitudes held to be important, while ethics are a set of morally-based beliefs which govern conduct. Very often, an ethical system will fail when confronted with a situation and force a choice between values.
In general, it is accepted that a just law must acknowledge the following characteristics: It is based on some form of ethical precept to which most subscribe,
It treats all people equally,
It aims to ensure contentment for the greatest number possible,
It aims to ensure community survival and wellbeing by stressing consensus and cohesion,
It allows for general principles to be mitigated in cases where mercy or sympathy are appropriate,
It aims to redress systemic inequalities by positive action,
It leaves people free,
It accounts for material limitation and
It can be invoked without undue delay or suffering.
It's crashing and burning! Crashing and burning!