Finnish war crimes, committed by the the Finnish armed forces, largely consisted of some cases of murder of POWs and ill-treatment of Soviet POWs in camps, up to and including murder. Where POWs, or enemy soldiers attempting to surrender, or wounded enemy soldiers, were murdered, there were very few prosecutions. The number of such cases is unknown, but, as in most armies, there were some. One anecdotal report of such an event ran as follows:
Officer A shoots Soviet POW for no apparent reason.
NCO B says "Sir, we're not meant to do that!"
Officer A starts shouting loudly at NCO B, waving his pistol around, accusing him of treason.
NCO B, fearing for his own life, empties his SMG into officer A. Witnesses agreed with the necessity of the action, and this was the end of the story.
POWs were killed for revenge, for being inconvenient to guard and feed, or to treat their wounds. Some POWs were killed because they refused to answer questions during interrogation. Officers were proportionally more likely to murder POWs than NCO and privates. Those with a Civil Guard background were more likely to murder POWs (but most regular army and reserve officers had a Civil Guard background, so this might not be any different from "officers being more likely").
Criminal charges were filed against 1381 Finnish POW camp guards, leading to 723 convictions and 658 acquittals. Some of these criminal charges had already been initiated by the Finnish authorities during the Continuation War - not all them were simply "victor's justice".
For more on these crimes, see:
In addition, much of the Finnish political leadership at the start of the Continuation War were charged with "crimes against peace", "planning, preparation, initiation, or waging of wars of aggression, or a war in violation of international treaties, agreements or assurances, or participation in a common plan or conspiracy for the accomplishment of any of the foregoing", which they had most certainly done, in the planning with Germany for the combination of the Continuation War and Operation Barbarossa.
The above crimes were tried by Finnish courts, with supervision by the Allied Control Commission and the Soviets, who sometimes interfered in the proceedings, but were more or less satisfied by the Finnish efforts to try their own war criminals.
In addition, on the 6th of November, 1942, Finland deported 27 foreign civilians to German-occupied Estonia. Most were Estonians were had fled to Finland. Eight were Jewish, one of whom was 2 years old. One of the Jews was reported to have fought for Finland during the Winter War. One of the Jews survived the war. "Those eight" are famously Finland's only deported Jews, but this ignores 4 Jews deported earlier than that, so "those eight" should be "those twelve". When the 6th November deportations were reported in the Finnish media, there was a shitstorm of protest, and no further deportations occurred (not counting end-of-war repatriations of Soviet POWs and Soviet citizens who had fled to Finland, some of who were promptly executed by Soviet authorities, and others sent to Siberia). For more on these deportations, see
Finally, about 1400 Finnish volunteers served in the Waffen-SS (in SS-Division Wiking). Germany had requested Finnish volunteers for the SS in the planning for the upcoming Operation Barbarossa and the Continuation War. Finland agreed. The individual volunteers were genuine volunteers, often strongly anti-Soviet. Some of these Finnish volunteers committed atrocities during their service. For more details, see: