Once the Crown proves the elements of a regulatory or provincial offence or otherwise establishes a duty upon the accused, the onus is on the accused to establish due diligence. This must be proven on a balance of probabilities.
Due diligence requires the accused to "take all reasonable steps" to avoid the harm that resulted. 
It is not necessary that the accused take all conceivable steps, however.
In assessing due diligence, WD test for credibility does not apply.
The accused must show that he took “all reasonable care” to avoid committing the offence.
This is considered from the perspective of a reasonable person in similar circumstances. This does not mean that the accused would be required to perform acts that would put the accused in unreasonable danger.
Industry Standards and Practices
Compliance with industry standard practice is a factor that weighs in favour of due diligence but it not determinative.
Industry standards and practice cannot be of any value to due diligence if it is established that the standard is insufficient. It then cannot be used as a shield against responsibility.
- e.g. R. v. Ariganello, 2013 ONCJ 13 (CanLII)
- R. v. British Columbia Hydro and Power Authority,  B.C.J. No. 1744 (S.C.), at para. 55 ("In other words, an accused must take all reasonable steps to avoid harm. However, that does not mean an accused must take all conceivable steps.")
- BC Hydro and Power Authority at para. 55
R. v. Carpentier 2005 MBCA 134 (CanLII) at para. 27
Ariganello at para. 18
R. v. Defaria  O.J. No. 5427, 2008 ONCJ 687 (CanLII) at para. 16
see R. v. Emil K. Fishing Corp.; R. v. Kukuljan, 2008 BCCA 490 (CanLII),  B.C.J. No. 2326; 304 D.L.R. (4th) 725 leave refused
R. v. Bui,  O.J. No. 1456(C.J.)
R. v. London Excavators & Trucking Ltd. reflex, (1997) 26 C.C.E.L.(2d) 132(Ont. P.C.)
R. v. Pilen Construction of Canada Ltd.  O.J. No. 5650, affd  O.J. No. 2980 (S.C.J.)
Libman, Regulatory Offences in Canada, at page 7-27 (“…a defendant cannot hide behind commonly accepted standards of care if, in the circumstances, due diligence warrants a higher level of care.”)