Common Traffic Offences
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c. “incapable of having proper control of the motor vehicle

This is probably the most difficult part of section 39: how do we determine whether a person is “incapable of having proper control of the motor vehicle”?  Of course, there can be objective evidence (usually supported by a medical report) such as an erratic manner of driving, the occurrence of an accident, the driver smelt of alcohol or was unable to walk in a straight line, etc.  But all these require evidence to prove and can be subject to heated argument from the defendant.

Section 39A of the Road Traffic Ordinance (Cap.374 of the Laws of Hong Kong) was passed in 1995 to overcome this unsatisfactory situation.  This section makes it an offence for any person “who drives or attempts to drive a motor vehicle, or is in charge of a motor vehicle, on any road with the proportion of alcohol in his breath, blood or urine exceeding the prescribed limit”; and “prescribed limit” is defined under section 2 of the same Ordinance as:

  • 22 micrograms of alcohol in 100 millilitres of breath;
  • 50 milligrams of alcohol in 100 millilitres of blood; or
  • 67 milligrams of alcohol in 100 millilitres of urine.

In light of this legislation, once there is proof of the alcohol level by way of breath, blood or urine, the prosecution could simply lay a charge under section 39A instead of section 39 in most drunken driving cases and does not have to worry about how to prove whether the driver is “incapable of having proper control of the motor vehicle”. 

However, section 39A deals only with alcohol, not drugs.  For cases related to taking drugs while driving, the prosecution would still have to produce sufficient evidence to show that the driver is “incapable of having proper control of the motor vehicle”.

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