Holyrood's increased powers for sheriffs does not matter as road traffic law is not devolved

He may have required some clever mental gymnastics to keep his audience on side but that was nothing compared to the intellectual feat performed by Lord Hope in the recent decision of the Supreme Court in the cases of Martin v HMA and Miller v HMA. These cases arose from relatively minor road traffic prosecutions but they have stirred up a tremendous amount of interest because of the differing views set out by Lord Hope and Lord Roger and the Holyrood v Westminster debate.

The cases arose after the Scottish Parliament increased the sentencing powers of sheriffs in summary proceedings to a maximum of 12 months imprisonment, with the Criminal Proceedings Act 2007.

No problem there, one would think. Perfectly at one with the Scotland Act. It came as a bit of a surprise to read Lord Hope stating: "To draw a line between statutory offences relating to reserved matters and those relating to matters that were not reserved would have been even more confusing. When they were dealing with an offence created by a UK statute, prosecutors and sheriffs would have to check in each case whether they were on the right side of the line."

Well tough, that's what lawyers have to do. I would check the provisions of the statute and the penalties applying thereto and I would expect the sheriffs and prosecutors to do the same.

When I see a reserved area of law with a specific penalty I can explain to my client that he might end up receiving that penalty.

Post Martin and Miller I have to explain in Scotland the penalty is higher than stated in the statute. I cannot see how this will help avoid confusion, especially among the English public who stray across the Border while disqualified from driving.

Lord Hope's logic is hard to fault and it would seem he has smoothed over the cracks of a possible Holyrood/Westminster trespass.

But Lord Rodger also puts it well, again with flawless logic, by stating: "It is true the purpose of section 45 is to increase the sheriff's sentencing powers. That is why s45 does not relate to reserved matters... increasing the sentencing powers of lower court judges is not a passport that entitles the Scottish Parliament to disregard the prohibitions in the other paragraphs of section 29(2) and to sweep aside the provisions of the Road Traffic Offenders Act."

Both faultless pieces of logic but Lord Hope carried the three to two majority decision.

It has been recognised that Westminster must be involved in this area as was demonstrated in the reform of the District Courts to Justice of the Peace courts where reform increased the sentencing power of magistrates to allow disqualification from driving for traffic offences. If it was concluded Westminster's authority was required for this increase in powers one would consider that authority would also be required to increase the sentencing powers of sheriffs in road traffic matters.

Sheriffs have always had the right to disqualify for 12 months for disqualified driving. The Crown simply require to raise the matter on indictment. The concern is that Holyrood has effectively passed legislation increasing sentencing powers of sheriffs at summary level that encroaches on to reserved statute.

By increasing powers on summary proceedings there will be a perceived likelihood of sentencing creeping up.

There may be nothing wrong in principle with creating differing sentences for the same crime, north and south of the Border, but I thought the whole point of "reserving" areas of legislation was to avoid confusion.

As a road traffic law specialist I get tired of explaining to people that road traffic law is not devolved. It now looks like I will have a wee bit more explaining to do in the future.

Graham Walker is a specialist at Road Traffic Law. www.roadtrafficlaw.com