Carrying offensive weapons is a criminal offence by virtue of section 47 of the Criminal Law (Consolidation) (Scotland) Act 1995 (“the 1995 Act” on this page):
In order to understand what exactly this offence requires, it’s helpful to break down subsection (1) into its constituent parts.
“has with him”
Note that this is not necessarily the same thing as “posseses”. In law, possession requires knowledge, whereas “has with him” only requires the presence of the object in close enough proximity to the accused.
“In Scotland it is clear…that the approach taken is that Parliament deliberately intended not to include such factors as knowledge and intent in the section and that therefore these matters are irrelevant to the initial question of whether someone has an item with him…
…The Scottish approach has been to factor in knowledge at the stage of considering whether the statutory defence is available…
…It is correct to say that a person can have an item with him without knowing of the item’s existence, at least if he ought to have been aware of it…”Lord Justice Clerk (Carloway), paragraphs 9, 10 & 11
What this means in practice is that the Crown does not need to lead evidence from which it can be inferred that the accused actually knew about the presence of the object in order to prove the charge. The question of whether the accused actually knew about it might come up in the context of “reasonable excuse” (see below), in which case the onus would be on the defence to establish it.
The words “has with him” mean that the object in question is readily available to the accused; the accused does not have to have the object in their hand or on their person.
Smith v Vannet [1998 SCCR 410]
The appellant had been convicted of a s47 offence and a s49 offence after a wooden cosh had been found under the front passenger seat of a parked car. A knife was found under the driver’s side floor mat. The appellant had been standing around six feet away from the car, with its keys in his pocket.
He appealled on the basis that he did not have the items “with him”, but his conviction was upheld on appeal.
“These weapons would have been readily available for the appellant for use…had he wished to make use of them. In our view…the sheriff was entitled to conclude that the appellant had the cosh and knife with him in the lane.”Lord Justice-General at page 413
“in a public place”
In short, s47(4) defines “public place” as anywhere that is not “domestic premises” (meaning a private dwelling, including its immediate surroundings such as its garden, garage or outhouse).
Places used by more than one dwelling (e.g. the stair of a block of flats, or a shared garden) are classed as public places according to this definition.
Schools and prisons are not included in the definition of “public place” for this offence, because there are distinct offences for having offensive weapons in schools (s49A of the 1995 Act) and in prisons (s49C).
The definition of “public place” in s47(4) seems to be extremely wide, but the wording of the definition is clear.
Even in cases where the accused has been found with a weapon in a place that any ordinary person would regard as non-public, the courts have taken the view that the accused will inevitably have carried the weapon through a public place in order to reach the non-public place. Provided the locus is defined to include the public place, then a conviction will likely stand.
Normand v Donnelly  SLT 62
This case predates the 1995 Act, but the relevant offence here (s1(1) of the Prevention of Crime Act 1953) was worded in a very similar way to s47 of the 1995 Act.
The appellant had been convicted of having a cleaver with him in a hospital emergency department. The cleaver had been found in his pocket in a private treatment cubicle.
It was agreed that the cubicle itself was not a public place, but the Appeal Court held that the sheriff was entitled to infer that the appellant must have carried the cleaver through the (public) reception area of the emergency department in order to reach the treatment cubicle, so the conviction was upheld.
When is an object an offensive weapon? “Offensive weapon” is defined in two distinct ways by s47(4):
The first way is as follows: “any article made or adapted for use for causing injury to a person”.
An article made…for causing injury includes what we might regard as “traditional” weapons. For example, shruiken (throwing stars), coshes and police batons would likely fall into this category.
Where an article has more than one purpose, then it is not an offensive weapon per se. In Woods v Heywood [1988 SCCR 434], a machete was held not to be an offensive weapon per se, since it could reasonably be regarded as a tool.
The characteristics of the particular item will have a bearing on whether it can be regarded as made for causing injury. In McKee v MacDonald [1995 SCCR 513], it was held that a lightweight and decorated “souvenir” police baton was not per se an offensive weapon since it could not realistically be compared to the real thing.
An article adapted for use for causing injury could include any number of ordinary objects modified in order to cause injury to a person. For example, driving nails through a baseball bat would constitute such modification. Similarly, deliberately breaking a bottle during a bar fight in order to increase its damage-dealing potential would likely count as adapting it in order to cause injury.
The second way is: “any article…intended, by the person having the article, for use for causing injury to a person by (i) the person having it, or (ii) some other person”.
This second definition can encapsulate almost any imaginable household or mundane object; it all depends on the intention of the person who has the object, which can be inferred from evidence of the circumstances.
For example, a normal biro pen could count as an offensive weapon in terms of this definition if the accused is brandishing it at someone else, in such a way that it can be inferred that they intend to stab the person with it.
In Skachill v MacLeod [2012 HCJAC 131], a screwdriver found in the accused’s pocket was held to be an offensive weapon in circumstances where the accused had acted aggressively towards police officers, and told one of them that he would stab them.
Defence: “reasonable excuse or lawful authority for having the weapon”
The s47(1A) defence is for the accused to establish, on the balance of probabilties (more likely than not).
“lawful authority” is included to protect (e.g.) police officers from prosecution for carrying weapons such as batons.
Whether an excuse is a reasonable excuse will depend on the particular facts and circumstances of the case.
In Grieve v MacLeod [1967 JC 32] it was held that a taxi driver carrying a weapon (a piece of rubber hose tipped with metal) out of a general fear of attack by customers is not a reasonable excuse, since the purpose of the applicable legislation was to ensure that the public do not take the law into their own hands.
The absolute apex of “reasonable excuse” cases is Frame v Kennedy:
Two police officers approached the accused, who appeared to be a fellow officer, outside a bar in Aberdeen. He was dressed in a very similar manner to Grampian police officers, including a utility belt with two batons and a spray canister attached.
The accused immediately volunteered that he was not a police officer, but a stripper, who had been booked to perform at the bar in a few minutes.
“The police officers decided to allow him to enter the premises…Both officers were of the view that it was important to ascertain the truth or otherwise of the respondent’s stated purpose of attendance at the premises. They, accordingly, attended within the Paramount bar and saw part of his performance. Both officers were satisfied that what they had been told by the respondent was true and genuine.” [paragraph 4]
Later, after the accused had voluntarily agreed to be interviewed by the police, he admitted that the canister contained “a defence dye” which he carried in case he was assaulted, because “drunk guys get very jealous of male strippers”.
The accused was charged with possession of offensive weapons. The sheriff acquitted him after a defence submission of “no case to answer”. The Crown appealled.
The Appeal Court upheld the acquittal, holding that “the reason for the respondent having the batons on his person was to add verisimilitude to his fancy dress, and that this amounted to a reasonable excuse for having them with him at the time in question.” [paragraph 24]