england-and-wales
Is this a defence?
Short Answer: Possibly, if "special reasons" apply. If not, it's a mandatory minimum of 6 penalty points (subject to below). A driving disqualification (i.e. ban) and/or a fine are also possible, but not mandatory.
Long Answer: The offence of allowing someone else to drive one's car without insurance falls under section 143(1)(b) Road Traffic Act 1988:
(b) a person must not cause or permit any other person to use a motor vehicle on a road or other public place unless there is in force in relation to the use of the vehicle by that other person such a policy of insurance as complies with the requirements of this Part of this Act.
This attracts a discretionary driving ban and/or fine, with a mandatory endorsement (i.e. penalty points) - see the Sentencing Council Guidelines
- Must endorse and may disqualify. If no disqualification impose 6- 8 points
Note there is a distinction between cause or permit and use. The latter has a statutory defence for certain drivers who believed incorrectly they had valid insurance1 unlike "causing or permitting" someone else to drive which does not.
There is, however, the potential for avoiding a ban and some/all of the penalty points if the court finds there are "special reasons" to do so. For example: if one can show that they carried out all reasonable steps and due diligence, or made it a pre-condition that the driver was properly insured.
- Re: Disqualification - The court may consider section 34(2) Road Traffic Offenders Act 1988:
(2) Where a person is convicted of an offence involving discretionary disqualification, and either—
- (a) the penalty points to be taken into account on that occasion number fewer than twelve...
...
the court may order him to be disqualified for such period as the court thinks fit.
- Re: Endorsement - The court may consider section 44 Road Traffic Offenders Act 1988:
(1) Where a person is convicted of an offence involving obligatory endorsement...
[...]
(2) Where the court does not order the person convicted to be disqualified, it need not make an order under subsection (1) above if for special reasons it thinks fit not to do so.
Whether a claim for"special reasons" is available will be fact-dependent.
1 For completeness, driving without valid insurance is at s.143(1)(a) RTA1988:
(a) a person must not use a motor vehicle on a road or other public place unless there is in force in relation to the use of the vehicle by that person such a policy of insurance as complies with the requirements of this Part of this Act...
The statutory defence for certain employees who do not have the required insurance is at s.143(3) RTA1988:
(3) A person charged with using a motor vehicle in contravention of this section shall not be convicted if he proves—
(a) that the vehicle did not belong to him and was not in his possession under a contract of hiring or of loan,
(b) that he was using the vehicle in the course of his employment, and
(c) that he neither knew nor had reason to believe that there was not in force in relation to the vehicle such a policy of insurance as is mentioned in subsection (1) above.