Both Scottish and English law have had the concept of the "reasonable person" for many years.
From the Criminal Justice and Licensing (Scotland) Act 2010:
38 Threatening or abusive behaviour
(1)A person (“A”) commits an offence if—
(a)A behaves in a threatening or abusive manner,
(b)the behaviour would be likely to cause a reasonable person to suffer fear or alarm, and
(c)A intends by the behaviour to cause fear or alarm or is reckless as to whether the behaviour would cause fear or alarm.
(2)It is a defence for a person charged with an offence under subsection (1) to show that the behaviour was, in the particular circumstances, reasonable.
P.S. Good luck with finding a definition of a "reasonable person" although the members of a jury are regarded as being collectively reasonable.