| In English jurisprudence, the highest test as to whether an action was blameless is whether a reasonable man in that position would have done the same thing. This test is considered "objective" in that it is imposed by the court from its own point of view, as opposed to the weaker, subjective, test of whether or not the party in question thought what they were doing was acceptable.
The test can be further broken down into one concerning a reasonable man with:
Actual knowledge
The standard is a reasonable man knowing the same things as the party in question. This might be termed a "semi-objective" test.
Constructive knowledge and notice
Constructive knowledge is information that the actor can be relied upon by third parties to posess. Events and circumstances may put a person "on notice"; a reasonable man would investigate further.
Hence the full "reasonable man" test is the action of a reasonable man having the knowledge that was actually posessed, knowledge that ought to have been possessed, constructive knowledge, and respecting statutory duties. There is a further twist in the tail: in different circumstances, a different kind of "reasonable man" is presumed, to reflect the kind of person that ought to put themselves in a given position. So, trustees investing trust property ought to act as "ordinary reasonable men of business". | 
