Joseph was born in Lafon, diocese of Juba, South Sudan, on 1st January 1939, to Peter Yala and Anna Acan, parents of 10 children, five sons and five daughters. He was baptised and confirmed by Father Cesare Gambaretto in 1951. He attended primary school in his native village, then entered the minor seminary of Okaru (Torit, Eastern Equatoria). He then moved to the Major Seminary of Tore (Yei, Central Equatoria) for some time, but the seminarians were forced to flee due to the dramatic political situation. During their escape, they meet some Comboni missionaries who were about to leave South Sudan after the expulsion decree from the Khartoum government (1964). Joseph spent a year in Kit (near Juba), but then reached Uganda where he completed his training at the Major Seminary of Lacor. And it was here that he matured his Comboni missionary vocation.
In December 1967, he was sent to Florence for two years of novitiate. On 9th September 1969, he took his first religious vows and was sent to the scholasticate in Verona for the first two years of philosophy. In 1970 he went to the international scholasticate in Rome to complete his theological training at the Pontifical Urban College of ‘Propaganda Fide’. On 23rd April 1972, he was ordained a priest in the church of Sant’Andrea, in Tivoli, by Bishop Guglielmo Giaquinta.
Shortly afterwards, he left Italy, destined for South Sudan, where, for a few months, he was vice-rector of the minor seminary of the diocese of Torit. At the end of 1973, he was assigned to the Terekela mission. From 1974 to 1977 he was deputy parish priest of Nalingoro-Kapoeta. In 1977 he was assigned to Mupoi as spiritual director of the Missionary Sisters of the Blessed Virgin Mary. He remained there until 1982.
In January 1983 he was sent to the Comboni province of Italy, assigned to the community of Bari for the missionary animation service of the diocese. In July 1986 he was sent to Eldoret, Kenya, for a pastoral course at the AMECEA Ggaba Pastoral Institute. In July 1987, the bishop of Torit, Msgr. Paris Taban, chose him as the Vicar General of the diocese, but he had to reside in Juba for security reasons. In July 1991, he went to Kampala, Uganda where he ministered at the parish of Mbuya.
On 1st January 1995, he was sent to South Africa, to the mission of Elukwatini, in the diocese of Witbank. For an entire year, he was engaged in studying the language and was then appointed local superior of the Comboni community, working in the apostolate and missionary animation. In 2004 he moved to the parish of Barberton, in the same diocese, but in July he had to go to Nairobi (Kenya) for medical treatment. Three months later, he returned to South Sudan, to Lomin. The following year he was elected provincial councillor.
In 2006 he went to Rome for a refresher course, then, for a year and a half, he had to stay in Verona, at the Centre for the Sick, for medical treatment. He then returned to South Sudan and was again Vicar General of the diocese of Torit, based in Juba. In 2011 he went to stay at the Comboni House in Juba, in charge of ministry.
In March 2016, he retired to Moroyok (Juba), to the prepostulancy community. There he spent his last years, until his return to the Father’s house on 19th December 2023.
«Joseph had many human qualities – writes Father Guido Oliana in his biography of Father Joseph – which he put at the service of his vocation as a Comboni missionary priest. He was a person who fearlessly said what he thought and believed. A man of principle. He always showed great courage in denouncing the injustices committed by the Arab government of Khartoum against the South Sudanese, risking his life several times. He was a man of great humanity. He had great leadership qualities and a great sense of responsibility. He had a profound spirituality, which showed in his spirit of prayer, patience and humility. He was also a committed priest, who intensely loved his religious consecration and his priestly identity." (Father Franco Moretti, mccj)