GENEVA—A Liberian rebel commander was sentenced in Switzerland to 20 years in jail on Friday for rape, killings, and an act of cannibalism, in one of the first ever convictions over the West African country’s civil war. The case was also Switzerland’s first war crimes trial in a civilian court. It involved 46-year-old Alieu Kosiah who went by the nom de guerre “bluff boy” in the rebel faction ULIMO that fought former President Charles Taylor’s army in the 1990s. Kosiah faced 25 charges including one where he was accused of eating slices of a man’s heart. He was convicted of that and all but four of the other counts, documents from the Swiss Federal Court showed. He was arrested in 2014 in Switzerland, where he had been living as a permanent resident. A 2011 Swiss law allows prosecution for serious crimes committed anywhere, under the principle of universal jurisdiction. A …