APPEAL COURT, HIGH COURT OF JUSTICIARY
Lord Justice Clerk
 HCJAC 48
XC34/14 and XC33/14
OPINION OF THE COURT
delivered by LORD CARLOWAY,
the LORD JUSTICE CLERK
APPEAL UNDER SECTION 74 OF THE CRIMINAL PROCEDURE (SCOTLAND) ACT 1995
SHIRWA ABDISAYED HAASHI and RAHIM ABUKA ABDI
HER MAJESTY'S ADVOCATE
Appellant (Haashi): U Dar, Solicitor Advocate; Beltrami & Co, Glasgow
Appellant (Abdi): J Keenan, Solicitor Advocate; Capital Defence Lawyers
Respondent: Niven-Smith AD; the Crown Agent
11 February 2014
 The appellants were indicted to a first diet on 29 October 2013 at Dumfries Sheriff Court with a trial diet fixed for 12 November 2013. They were charged with, amongst other things, concern in the supplying of cannabis, cocaine and heroin on 9 December 2012 on the A74(M) Gretna to Glasgow road, near the Gretna junction. The first diet was continued until 5 November, when agents for both appellants were allowed to lodge preliminary issue minutes. The first diet was then continued until the trial diet.
 On 12 and 18 November 2013, the sheriff heard evidence relating to the minutes, which contained objections to the admissibility of the evidence of the search of the car in which the appellants were travelling. This was on the basis that, when the appellants were detained in terms of section 23 the Misuse of Drugs Act 1971, the officers detaining them did not have reasonable grounds for suspicion that they were in possession of controlled drugs.
 The evidence heard by the sheriff was in short compass. Two police officers, on uniformed mobile traffic patrol in the early hours of 9 December 2012, had received information from their force control regarding a black Vauxhall Meriva being a "vehicle of interest". This meant, in their minds, that this was a car that they were to look out for. One of the officers spoke to the information also being that the car was involved in the supplying of controlled drugs, although the other officer did not recall that. The first officer took the phrase "vehicle of interest" to mean that it had been the subject of surveillance.
 The officers spotted the car and started north in their own vehicle, with a view to stopping it. They said that the purpose of that procedure was for a routine road traffic check, in terms of section 163 of the Road Traffic Act 1988. The sheriff, having heard the evidence, accepted that this had been their motivation and that it had not been their intention, prior to stopping the car, to search it for the presence of drugs. When the first officer spoke to the driver through the passenger window, which had been opened, he said that he noticed a "strong smell of cannabis". He became concerned that there might be drugs in it. The other officer spoke to noticing the same smell when he went to speak to the front seat passenger. Having consulted with each other, they both agreed that they had smelled cannabis. They decided that they would call for assistance, as there were 5 people in the car, detain the occupants and search the car under section 23 of the 1971 Act.
 During the course of the testimony of the police, there was cross-examination on a variety of different topics, but ultimately the sheriff did not consider there was any reason to disbelieve what the officers had said about the reason for stopping the car and about the nature and reasonableness of the suspicion which had arisen only once they had stopped it. He accordingly repelled the objections in respect of the recovery of drugs said to have been found in the car.
 The appellants sought leave to appeal. This was granted by the sheriff. The reasons for doing so are not evident (see infra). The Notes of Appeal were lodged. That for the first appellant contained no grounds of appeal at all. That for the second appellant did contain a ground, but all that it said was essentially that the sheriff had erred in holding that the officers had reasonable grounds for their suspicion. The nature of the error was not specified.
 Whether a police officer suspects that a person is in possession of a controlled drug, in terms of section 23(2) of the Misuse of Drugs Act 1971, and whether that suspicion can be categorised as reasonable, are both matters of fact which are primarily for the court of first instance to resolve having been informed of the relevant facts, or having heard the relevant evidence. In this case the sheriff believed the officers that they had stopped the car in terms of the provisions of the Road Traffic Act and had only decided to proceed under section 23 once they had smelled the cannabis. That was essentially an end of the matter, unless it could be said that the sheriff had erred in some way in his assessment of the evidence or had misdirected himself in law. There does not appear to be any basis for holding that there has been any such error on the part of the sheriff. None is evident from the Notes of Appeal and the submissions did not advance matters beyond a contention that the sheriff should have reached a different conclusion having regard to the existence of the information from force control. The appeals are accordingly refused.
 It remains for the court to express its surprise that leave to appeal was granted in a case which involved a simple assessment of the credibility and reliability of police officers. The sheriff adequately explained his decision in this regard. An appeal from a decision taken pendente processu is an extraordinary application; that is why there is a requirement for leave from the court of first instance. Such appeals were introduced into solemn procedure by the Criminal Justice (Scotland) Act 1980 (sch 4, para 5), which established the optional diet and permitted appeals from decisions taken at them (Criminal Procedure (Scotland) Act 1975, ss 76 and 76A) following upon the recommendations of the Thomson Committee (second report, cmnd 6218, 1975 para 30.08.09; third report, cmnd 7005 para13.09, recommendation 71). The requirement for leave may have been a governmental innovation. Be that as it may, the requirement for first instance leave is not to be confused with that for leave against conviction, where a low threshold of arguability is statutorily provided (1995 Act, s 107(1)).
 A degree of care is required when determining whether leave to appeal from a preliminary decision should be granted, especially where the decision has been a discretionary one or one primarily for the judgment of a first instance court, depending upon particular facts and circumstances, rather than one involving a point of law (see eg Reid v HM Advocate 1984 SLT 391, LJG (Emslie) at 392; Hogg v HM Advocate 1998 JC 142, LJG (Rodger) at 146). This is because an appeal at the preliminary stage will inevitably disturb the standard procedure leading to trial. Although there is no statutory restriction on the circumstances in which leave might be granted (and they may be highly variable), leave should not normally be granted at the preliminary stage unless the court is satisfied that the appeal has a realistic prospect of success and that it is in the interests of justice that the point taken be resolved in limine as a matter of practicality rather than being advanced (if still relevant) after the trial. The court is unable to see what point could have been taken in this case which could have had any such prospect.