R. v. Gupta does not indicate that the person not wearing a seatbelt was under 16-years of age. I assume they were under 16, though, because a driver is not responsible for a person over 16-years of age.
However, I don't see how they were convicted under s. 106(6). Section 106(6) is an exception to ss. (2) and (3) clause. Subsection (2) only applies to the driver wearing a belt and ss. (3) only applies to a person who is at least 16 years old, for which the driver is not responsible.
If the passenger was under the age of 16, then 106(4) applies. Not 106(6).
This case is easily winnable on appeal.
Seat belt assembly must not be removed or altered
106. (1) No person shall drive on a highway a motor vehicle in which a seat belt assembly required under the Motor Vehicle Safety Act (Canada) at the time that the vehicle was manufactured or imported into Canada has been removed, rendered partly or wholly inoperative, modified so as to reduce its effectiveness or is not operating properly through lack of maintenance. 2006, c. 25, s. 1.
Use of seat belt assembly by driver
(2) Every person who drives on a highway a motor vehicle in which a seat belt assembly is provided for the driver shall wear the complete seat belt assembly as required by subsection (5). 2006, c. 25, s. 1.
Use of seat belt assembly by passenger
(3) Every person who is at least 16 years old and is a passenger in a motor vehicle on a highway shall,
(a) occupy a seating position for which a seat belt assembly has been provided; and
(b) wear the complete seat belt assembly as required by subsection (5). 2006, c. 25, s. 1.
Driver to ensure young passenger uses seat belt assembly
(4) No person shall drive on a highway a motor vehicle in which there is a passenger who is under 16 years old unless,
(a) that passenger,
(i) occupies a seating position for which a seat belt assembly has been provided, and
(ii) is wearing the complete seat belt assembly as required by subsection (5); or
(b) that passenger is required by the regulations to be secured by a child seating system or child restraint system, and is so secured. 2006, c. 25, s. 1.
How to wear seat belt assembly
(5) A seat belt assembly shall be worn so that,
(a) the pelvic restraint is worn firmly against the body and across the hips;
(b) the torso restraint, if there is one, is worn closely against the body and over the shoulder and across the chest;
(c) the pelvic restraint, and the torso restraint, if there is one, are securely fastened; and
(d) no more than one person is wearing the seat belt assembly at any one time. 2006, c. 25, s. 1.
Exception (6) Subsections (2) and (3) do not apply to a person,
(a) who is driving a motor vehicle in reverse;
(b) who holds a certificate signed by a legally qualified medical practitioner certifying that the person is,
(i) for the period stated in the certificate, unable for medical reasons to wear a seat belt assembly, or
(ii) because of the persons size, build or other physical characteristic, unable to wear a seat belt assembly; or
(c) who is actually engaged in work which requires him or her to alight from and re-enter the motor vehicle at frequent intervals and the motor vehicle does not travel at a speed exceeding 40 kilometres per hour.