Oikeudenkäymiskaari (4/1734), 17 luku 1 §.

Oikeudenkäymiskaari — Chapter 17

Oikeudenkäymiskaari (4/1734), 17 luku 1 § — Todisteiden esittäminen ja arviointi.
The court must assess the evidential value of the evidence presented and other circumstances arising in the proceedings, and decide what has been proved or remains unproved. The law adopts free evaluation of evidence, unless otherwise provided.

17 luku 2 §.
This section sets out the general burden-of-proof rules for civil cases; it should not be cited as the criminal-case burden-of-proof provision.

17 luku 3 § — Näyttö rikosasiassa.
In a criminal case, the party bringing the punishment claim must prove the facts on which that claim is based. A conviction requires that no reasonable doubt remains about the defendant’s guilt.

An alleged instrument and physical possibility

These provisions do not prescribe a universal list of object details such as manufacturer, model, length, width, height or weight. They do require the court to decide what has been proved on the evidence, and they place the burden of proving the facts supporting the criminal charge on the prosecution.

Where the prosecution’s account depends on a particular object passing through a doorway or moving around obstacles, the object’s dimensions and the relevant spatial measurements may be material facts. The question is whether the evidence presented sufficiently establishes those facts and supports the alleged movement. If the dimensions or the object’s identity are uncertain, the uncertainty must be assessed in the context of the complete evidence; this section does not itself create a mandatory measurement protocol.

• What evidence establishes the alleged object’s identity and dimensions?
• What evidence establishes the dimensions of the doorway and the positions of obstructions?
• Does the court explain what was proved about the object and the alleged trajectory?
• Were relevant uncertainties addressed in the reasoning?
• Does the evidence as a whole establish the alleged factual sequence beyond reasonable doubt?

The Finnish statutory text linked above is authoritative. This post summarises the relevant provisions and does not assert that the law always requires the object itself to be produced, photographed or measured.