Related Rule
Finland
Practice Relating to Rule 77. Expanding Bullets
At the CDDH, Finland stated that it “attached the greatest importance to the prohibition of dum-dum bullets in The Hague Declaration of 1899”. 
Finland, Statement at the CDDH, Official Records, Vol. VI, CDDH/SR.44, 30 May 1977, p. 285, § 34.
Finnish police are reported to have used hollow-point handgun bullets since 1994. 
Jorma Jussila and Ralph Wilhelm, “Sicher und wirksam: Munition der finnischen Polizei”, Deutsches Waffen Journal, No. 9, 2000, p. 132.
According to an article by the Finnish Senior Advisor of the Weapons Technology Police Technical Centre, the use of hollow-point expanding handgun bullets presents some advantages, such as the avoidance of danger to bystanders through over-penetration of the bullet or ricochet. The article’s author emphasizes the existence of “a very common misunderstanding”, which is that hollow-point handgun bullets cause much more tissue damage than non-deforming full metal jacket bullets. He states: “The truth, is, however, that a well designed expanding bullet causes less damage than some non-deforming full metal jacket bullet. This is because the latter starts tumbling causing an effect similar to that of an expanding bullet.” He adds:
Even when lethal ammunition are used some injury avoidance criteria must, however, be met. A bullet shall have consistent and controlled penetration thus minimising danger to bystanders while yet providing sufficient penetration in all circumstances. This is technically not possible without some braking mechanism like expansion or terminal ballistic instability. A bullet shall not cause more injury than is unavoidable. It shall not break up to fragments upon impact with soft tissue even when shot through various materials. A bullet shall have controlled trajectory. Upon impact with hard surface it shall not turn into excessively dangerous ricochets and the ricochets must not deflect significantly from the impact surface tangent. 
Jorma Jussila, “Future Police Operations and Non-Lethal Weapons”, Medicine, Conflict and Survival, Vol. 17, No. 3, July–September 2001, p. 259.