* Mother and son sentenced to life
* Guilty of rape as a crime against humanity
(Adds new court quotes, background)
By Fumbuka Ng'wanakilala
DAR ES SALAAM, June 24 (Reuters) - The U.N. war crimes tribunal for Rwanda sentenced former minister Pauline Nyiramasuhuko to life in prison on Friday, the first time a woman has been found guilty of genocide by an international court.
The International Criminal Tribunal for Rwanda (ICTR) found Pauline Nyiramasuhuko and her son, Arsene Shalom Ntahobali, who was also jailed for life, guilty of atrocities committed in Rwanda's southern Butare region during the 1994 massacre.
"The chamber convicts Pauline Nyiramasuhuko of conspiracy to commit genocide, crimes against humanity, extermination, rape, persecution and ... and violence to life and outrages upon personal dignity," read the ruling by the trial's three judges.
"She is sentenced to life imprisonment."
Nyiramasuhuko, 65, and a former families minister, was found guilty of seven out of 11 charges. The trial lasted 10 years.
Ethnic Hutu militia and soldiers butchered 800,000 minority Tutsis and politically moderate Hutus over 100 days between April and June 1994.
In its verdict, the court said Nyiramasuhuko was guilty of genocide and extermination as a crime against humanity for ordering the killing of scores of Tutsis taking refuge from the slaughter at a local government office in Butare.
"Hoping to find safety and security, they instead found themselves subject to abductions, rapes, and murder. The evidence ... paints a clear picture of unfathomable depravity and sadism," said the judgment read out by presiding Judge William Sekule.
The tribunal, based in Arusha, northern Tanzania, had allowed the rape charge to be added on grounds that the accused knew her subordinates were raping Tutsi women and failed to take measures to prevent or punish them.
"It's shocking that this mother and former social worker, trained to protect life, could instead have been responsible for such appalling crimes," said Freddy Mutanguha, Rwandan Country Director for the Aegis Trust, the genocide prevention organisation responsible for the Kigali Genocide Memorial.
Nyiramasuhuko and Ntahobali were tried alongside four co-accused, all local officials from the same southern region in a case dubbed the "Butare trial".
The tribunal pronounced all four guilty of genocide-related crimes, handing down jail terms of between 25 years and life.
Rwanda's Prosecutor General Martin Ngoga welcomed the sentence and said it would offer relief to survivors.
The tribunal was set up in November 1994 and has completed more than 50 cases, of which 19 are on appeal. Nine of those most wanted by the court's prosecutors are still at large.
The tribunal has been dogged by allegations of soaring costs and excessive bureaucracy. (Additional reporting by Kezio-Musoke David in Kigali; Writing by Richard Lough; Editing by David Clarke and Philippa Fletcher) (For more Reuters Africa coverage and to have your say on the top issues, visit: http://af.reuters.com)