R. v. Lohidici, 2005 ABPC 171:
 On the meaning of “obstruct”, the Criminal Code does not assist us. As is the case for many of the Code’s other terms, no definition is contained in the legislation. The invariable starting point of all judicial discussion is Hinchliffe v. Sheldon  3 All E.R. 406, wherein Lord Goddard posits, at p.408:
“Obstructing means, for this purpose, making it more difficult for the police to carry out their duties.”
 The Hinchliffe test has been variously considered, applied, softened, melded and massaged to the point where, in my view, the state of the law on obstruction in Alberta can generally be summarized along the following lines:
1. The question of whether the accused’s conduct constitutes “obstruction” is one of fact, to be determined having regard to all the circumstances of the specific case. R.v. Bull  A.J. No. 1673 (ABPC) at p 20, para 30.
2. It is not necessary that the constable be completely thwarted in the execution of his or her duty. Actions of the accused which, without lawful excuse, “impede”, “affect”, or make “more difficult” the peace officer’s work are considered “obstruction”. R.v. Bull, supra at p. 30, para 44. R.v. Whalen (1993) 143 A.R. 234 at p. 237-8.
3. Trifling, momentary or transitory actions on the part of the accused, which do not cause problems of consequence or which require only an insignificant amount of additional effort on the part of the peace officer, may not be sufficient to constitute “obstruction”. R.v. Whalen, supra at p. 237-8.
 In my view, Mr. Lohidici’s actions at the accident scene were neither trifling nor momentary. They clearly impeded, affected and made the officers’ work that day more difficult. Not only was his disruptive behaviour upsetting to the public, the police and the fire and EMS crews, it was dangerous, having regard to the fluid spills caused by the accident. Even more obstructive, however, were his actions in removing, and continuing to remove after being warned, evidence relevant to the impaired driving investigation being conducted by Constables Luxen and MacGillivary. I find that the accused’s actions obstructed the peace officer in the lawful execution of his duty. I now turn to the issue of intent.
MENS REA AND THE ACCUSED’S INTENTIONS:
 Parliament, through s.129 (a), intended to limit the actions of a citizen toward peace officers in the execution of their duty. The crime of obstruction, however, is less serious than many other offences in the Code. As a result, the courts have interpreted the offence as requiring a lower form of mens rea. R.v. Gunn, 1997 ABCA 35 (CanLII), (1997) 113 C.C.C. (3d) 174 (Alta. C.A.).
 It is settled law that s.129 (a) is an offence of general, as opposed to specific, intent. (R.v. Gunn, supra). Proof of intent is inferred from the commission of the act on the basis of the principle that a person intends the natural consequences of his or her act.(R.v. Daviault, 1994 CanLII 61 (SCC),  3 S.C.R. 63 at p. 123 (Sopinka, J. in dissent)). Where the accused’s actions are deliberate, or “wilful”, that is, he knows what he is doing, intends to do it and is a free agent, the mens rea necessary to support a conviction under s.129 (a) is present. (R.v. Goodman (1951), 99 C.C.C. 366, 2 W.W.R. (N.S.) 127 (B.C.C.A.); R.v. Westlie reflex, (1971), 2 C.C.C. (2d) 315,  2 W.W.R. 417 (B.C.C.A.); R.v. Gunn, supra; R.v. Johnsgaard  A.J. No. 1234 (A.B.P.C.) at para. 13.