In the 2012 Summer Paralympics in London, Siaffa became the first athlete to represent Liberia in the Paralympics. He also served as the flag bearer for his country in the parade of nations. Ultimately, on 4 September 2012, Siaffa ranked 7th in the men's 82.5 kg powerlifting event. There, he achieved his personal record, benching 419 lbs. In 2016, Siaffa wrote a letter to the International Paralympic Committee outlining his dissatisfaction with the Liberia National Paralympic Committee (LNPC). The letter alleged that while he was willing to compete in the Paralympics in Rio that year, he was uncomfortable with the leadership of the LNPC, and had faced verbal abuse among other poor treatment at their hands. LNPC General-Secretary Festus Robinson, who was one of the officials accused of abuse, accused Kotie Mawolo, with whom he had long standing conflict, of being the true author of the letter. Robinson believed that Mawolo had only gotten Siaffa to sign it. Liberia did not end up competing in the 2016 Paralymic Games, as the government was unable to provide the funds for the trip.