As part of the offence of "Over 80" under s. 253(1)(b), the crown must prove the accused's Blood Alcohol Content (BAC) is over 0.08 per millilitres.
Under s. 254(3), a sample of breath, urine or blood can be taken for measurement. The sample can be analysed and a blood alcohol level can be measured. This measurement can be used to infer the BAC level at the time that the accused was operating a motor vehicle.
The procedure required for a proper demand under s. 254(3) must be followed. The taking of a sample counts as a search and if the procedure is not followed then it will amount to a search not authorized by law, and therefore violate s. 8 of the Charter. Section 254(3) sets the constitutional minimum requirement for a search.
The timing of the sample is of great importance. The timing must be in relation to the time in which the accused was in care and control of the vehicle and in relation to the time where the officer initially forms grounds of suspicion and belief.
Most details of the demand, such as who asked for the demand or where it was made, are not essential to prove. There only needs to be evidence that the demand was made with sufficient grounds as soon as practicable.
Under s. 254(3), a peace officer may demand an Intoxilyzer breath sample where the officer has “reasonable and probable grounds” to believe that the person is committing, or has committed in the last three hours, an impaired driving offence.
Outside 3 Hours Window
Where the officer has not made a demand for a screening sample under s. 254(2)(b) or a demand for a breath sample in an approved device under s. 254(3), the officer may still make a demand under s. 254(3.3):
"Reasonable grounds to believe"
Blood or Breath Sample Demand
The demand informs the accused of the intention to take a sample of blood or breath. A typical sample demand under s. 254(3) will go as follows:
The demand must be in plain language, sufficient for the accused understand what is required of them.  There is no fixed formula or magic wording, rather sufficiency can be inferred on the surrounding circumstances of the demand. 
A variety of variations on demand are available.
The key requirement is that the demand not is an invitation or request. It must be unequivocal. 
There is no requirement that the word "forthwith" be used, but the meaning must be conveyed by word or conduct.
It is not more restrictive or meaningful to say "sample" instead of "samples."
Whether the demand was unequivocal is a question of fact.
The demand should always involve an advisement that the sample will be taken by a qualified practitioner.  However, it is not necessary to inform the accused of all requirements regarding qualified medical practitioners.
A Breathalyzer demand can be made at any location and need not be at the location of the approved machine.
The officer should take steps to ensure that the accused understands the questions of the demand and is able to respond in a meaningful way.
The validity or invalidity of a second demand made by the Qualified Technician does not affect the validity or invalidity of the initial demand of the investigating officer and vice versa.
It is generally sufficient evidence for the officer to give testimony that a "breath demand" was made without giving a full verbatim reading of what was said.
- R v Harasym, 2008 ABQB 649 (CanLII), 461 AR 181, per McIntyre J, at para 30
R v Nicholson, 1970 CanLII 1094 (NS CA), (1970) 8 CCC (2d) 170 (NSCA), per McKinnon CJ - no special words are needed, only must be clear that there is no choice
R v Flegel, 1972 CanLII 1332 (SK CA), (1972) 7 CCC (2d) 55 (SKCA), per Culliton CJ
R v Boucher (1986) 47 MVR 173 (SKCA)(*no CanLII links)
R v Langdon, 1992 CanLII 2776 (NL CA), 74 CCC (3d) 570, 16 WCB (2d) 571 (Nfld. C.A.), per Goodridge CJ
R v Phelan, 1997 CanLII 14611 (NL CA), Nfld. & PEIR 169, 35 WCB (2d) 175 (Nfld. C.A.), per Green JA, at paras 12 and 13
R v Truscott, 2009 BCSC 364 (CanLII), per Warren J, at paras 19 and 20
R v Ghebretatiyos (2000), 8 MVR (4th) 132, 48 WCB (2d) 365 (Ont. Sup. Ct. J.)(*no CanLII links) , at para 19
A.-G. Alta v Kozicky, 1972 CanLII 1425 (AB QB), 9 CCC (2d) 146, per Sinclair J, at p. 149,  6 WWR 623, at p. 626
R v Rentoul, 1977 CanLII 1927 (AB QB), 37 CCC (2d) 78 (Alta. S.C.T.D.), per MacDonald J, at p. 83
R v Showell, 1971 CanLII 512 (ON SC), 4 CCC (2d) 252, per Haines J, at p. 255,  3 OR 460, 15 CRNS 305, at p. 308(“For a demand to be made pursuant to s. 223(1) [now s. 235(1)] it is sufficient merely for the officer to say he is asking for a breath sample pursuant thereto.”)
e.g. R v Bourns,  OJ No 2687 (Ont. Gen. Div.) (*no CanLII links)
R v McKeen, 2001 NSCA 14 (CanLII), 151 CCC (3d) 449, per Flinn JA (2:1)
R v Dotremont, 2011 MBQB 88 (CanLII), MVR (6th) 239 (Man. Q.B.), per Dewar J
R v Boucher (1986), 47 MVR 173 (N.B.Q.B.)(*no CanLII links)
, at p. 176
Nicholson, supra - no special words are needed, only must be clear that there is no choice
- R v Torsney, 2006 CanLII 18732 (ON SC),  OJ 2228 (ONSC), per Hawkins J
- R v Rentoul, 1977 CanLII 1927 (AB QB), (1977) 37 CCC (2d) 78 (ABQB), per McDonald J
R v Barwick, 2009 QCCA 458 (CanLII),  QJ 1876 (QCCA), per curiam
- R v Jackson, 2005 ABQB 268 (CanLII), 381 AR 294, per Marceau J, at para 47
- R v Barrett, 2012 NLCA 12 (CanLII),  NJ 61 (CA), per Welsh JA
- R v Kitchemonia, 1973 CanLII 888 (SK CA),  5 WWR 669 (SKCA), per Culliton CJ
- R v Squires, 2002 CanLII 44982 (ON CA), 166 CCC (3d) 65, per MacPherson JA, at para 32
- R v Townsend, 2007 ONCA 332 (CanLII),  OJ 1686 (CA), per curiam
R v Stewart, 2009 CanLII 11 (ON SC),  OJ 11, per Ross J
R v Benson,  OJ 3056 (ONSC)(*no CanLII links)
R v Tash, 2008 CanLII 1541 (ON SC),  OJ 200, per Hill J
R v Antoniak, 2007 CanLII 53233 (ON SC),  OJ 4816, per Garton J
Timing of demand ("as soon as practicable")
A breath demand amounts to a warrantless search and so is prima facie unreasonable, thus the burden is on the Crown to establish the validity.
Under s. 254(3), "as soon as practicable" means "within a reasonably prompt time" given the circumstances.
The inquiry is upon "whether the police acted reasonably." There is no need for the police to explain every minute that that the accused is in custody. Instead, the judge should use common sense and experience for determining practicality.
When delays exist due to the offs are performing other duties, the question for the judge is not simply weather there exists "some explanation" but rather weather "the steps taken by the office or in performing general duties before the demand was made were necessary and reasonable in the circumstances."
Where the investigating officer failed to make a valid demand, the qualified technician can still make a valid breath demand. The qualified technician must have the same requisite grounds and must make the demand "as soon as practicable" upon getting the grounds.
Waiting for a tow truck may result in too much delay. It is incumbent upon the officer to keep up to date on the availability of a tow truck and consider options such as calling for assistance in the case of a delay in its arrival.
- Right to Counsel
It is necessary that before the demand is made that the accused is given the right to counsel. This is particularly necessary where a refusal of the demand would be an incriminating statement.
- R v Breland, 2011 SKPC 54 (CanLII), 373 Sask R 130, per Gray J at 22
R v Squires, 2002 CanLII 44982 (ON CA), OR (3d) 765, per MacPherson JA
R v Phillips, 1988 CanLII 198 (ON CA), 42 CCC (3d) 150, per Blair JA at 156
- R v Vanderbruggen, 2006 CanLII 9039 (ON CA), 206 CCC (3d) 489, per Rosenberg JA, at paras 12 and 13 (the “touchstone for determining whether the tests were taken as soon as practicable is whether the police acted reasonably”)
See R v Letford, 2000 CanLII 17024 (ON CA), 150 CCC (3d) 225, per Goudge JA, at para 20
R v Seed, 1998 CanLII 5146 (ON CA),  OJ No 4362 (CA), per curiam, at para 7
R v Cambrin, 1982 CanLII 353 , per Craig JA at 61-3
R v Carter, 1981 CanLII 2063 (SK CA), 59 CCC (2d) 450 (Sask CA), per Culliton CJ
- Carter, ibid.
- R v Memisevic, 2010 BCSC 203 (CanLII), BCJ No 2299, per Dillon J
R v Chilton,  OJ 3655 (SC) (*no CanLII links)
R v Gill, 2007 CanLII 44826 (ON SC),  OJ 4098, per Langdon J, at paras 37 to 40
R v Dhaliwal, 2005 CanLII 8716 (ON SC),  OJ 1129, per Durno J, at paras 23 to 26
e.g. R v Dion, 2010 SKPC 76 (CanLII), SJ No 338, per Meekma J, 32 min wait for tow truck too long
R v McGonigal, 2011 ABPC 183 (CanLII), per Barley J - judge suggests that officer failed to keep track of delays in tow truck. violation found for 45 min delay.
R v Johnson, 2008 ABPC 225 (CanLII), 177 CRR (2d) 269, per Daniel J - 27 min delay was acceptable. Officer believed assistance not available that evening
R v Budgell, 2007 ABPC 138 (CanLII), AR 313, per Fradsham J, 25 min wait for truck unreasonable where officer did not checking if other officers could help
R v Hendsbee, 1995 CanLII 4164 (NS SC), 432 APR 236, per Tidman J
see also Right to Counsel