What is Evasion?

Legal Definition
In law, the Doctrine of Evasion is a fundamental public policy. Whereas a person may legitimately plan affairs so as to avoid the incidence of obligations or liabilities imposed by the law, no one is allowed to evade the operation of otherwise mandatory provisions once duties and liabilities have been properly imposed or incurred. It is also a common principle in conflict of laws.
-- Wikipedia
Legal Definition
A subtle device to set aside the truth, or escape the punishment of the law; as if a man should tempt another to strike him first, in order that he might have an opportunity of returning the blow with impunity. He is nevertheless punishable, because he becomes himself the aggressor in such a case. Wishard, 1 H. P . C. 81 Hawk. P. C. c. 31, §24, 25; Bac. Ab. Fraud, A.

2. An escape from custody.
-- Bouviers Law Dictionary
Legal Definition
A subtle endeavoring to set aside truth or to escape the punishment of the law. This will not be allowed. If one person says to another that he will not strike him, but will give him a pot of ale to strike first, and, accordingly, the latter strikes, the returning the blow is punishable; and, if the person first striking is killed, it is murder, for no man shall evade the justice of the law by such a pretense. 1 Hawk. P. C. 81. So no one may plcad Ignorance of the law to evade it. Jacob.
-- Black's Law Dictionary