Hamza al-Mustapha was the Chief Security Officer (CSO) of General Sani Abacha, military head of state of Nigeria from November 1993 to June 1998. After Abacha's death he was arrested and tried for murder and attempted murder of Kudirat Abiola. On 30 January 2012, a Lagos High Court sitting at Igbosere convicted Major Hamza Al-Mustapha over the murder of Kudirat Abiola, the wife of the acclaimed winner of the June 12, 1993 Presidential election, Chief Moshood Abiola. He was also sentenced to death by hanging but was discharged and acquitted of the crime by the appeal court, Lagos division on Friday, July 12, 2013. The appellate court said there was not enough evidence to incriminate Al-Mustapha in the murder of the Late Kudirat Abiola. On 12 July 2013, The Court of Appeal in Lagos discharged and acquitted Hamza Al-Mustapha from the murder of Kudirat Abiola. The verdict overturned that of the Lagos High Court which sentenced him to death by hanging. The presiding judge, Justice Rita Pemu, accused the lower court jude, Justice Mojisola Dada, of being ‘‘stroked to secure a conviction by all means.’’ Consequently setting Al-Mustapha free.
Al-Mustapha joined the army and was trained as an intelligence operative. He was involved in at least two investigations of coup attempts. His conduct of interrogations brought him to the attention of Sani Abacha. When Abacha was Chief of Army (August 1985 – August 1990) al-Mustapha was his Aide-de-Camp.
Hamza al-Mustapha was appointed Chief Security Officer to the Head of State (CSOHS) with a Special Strike Force Unit during Abacha's military regime (17 November 1993 – 8 June 1998). Other security outfits at the time were the Office of the National Security Adviser under Ismaila Gwarzo, the Directorate of Military Intelligence, the State Security Service and the National Intelligence Agency. All of these units engaged in extrajudicial killings of people seen as threats to the regime. Both Ibrahim Babangida and Sani Abacha gave Captain (later Major) Hamza al-Mustapha exceptional power, considerably greater than other officers who were nominally his superior.
After being appointed Chief Security Officer, Al-Mustapha established a number of small security outfits recruited from the military and other security organizations, and trained in Israel and Korea. Abacha's National Security Adviser Ismaila Gwarzo and al-Mustapha were said to be responsible for much of the "torture, killing and wanton looting" during Abacha's rule. On the orders of Sani Abacha's wife Maryam, al-Mustapha detained and tortured several women suspected to be Abacha's girlfriends. As head of the State Security Service (SSS) al-Mustapha was also said to be involved in drug trafficking, using diplomatic pouches to transport the drugs. 
Al-Mustapha was quickly removed from his job by the transitional regime established by General Abdulsalam Abubakar after Abacha's sudden death in June 1998. In October that year he appeared in court with Abacha's son Mohammed, charged with the murder in June 1996 of Kudirat Abiola, wife of the presidential candidate M.K.O. Abiola (who had died in jail in July 1998). At the trial the killer, Sergeant Barnabas Jabila, said he was obeying orders from his superior, al-Mustapha. Al Mustapha and four others were also charged with a 1996 attempt to murder Alex Ibru, publisher of The Guardian and Abacha's Minister of Internal Affairs. Another charge was laid against al-Mustapha for the attempted murder of former Naval chief Isaac Porbeni.
While the trials proceeded, al Mustapha was detained at the Kirikiri maximum security prisons. While imprisoned, on 1 April 2004 he was charged with being involved in a plot to overthrow the government. Allegedly he had conspired with others to shoot down the helicopter carrying President Olusegun Obasanjo using a surface-to-air missile that had been smuggled into the country from Benin. In 2007, there were appeals for al Mustapha's release by four newspapers and by former head of state Ibrahim Babangida. Eventually, after 12 years of imprisonment, trials and retrials, al-Mustapha and his co-defendants were acquitted of most charges on 21 December 2010. The co-defendants were former Lagos State Police Commissioner James Danbaba, former Zamfara State military administrator Jibril Bala Yakubu and former head of the Aso Rock Anti-Riot Police Rabo Lawal.
However, al-Mustapha was still not cleared of the alleged murder of Kudirat Abiola, for which he was being tried separately. In May 2011 there were rumors that al-Mustapha had been murdered at the Kirikiri Maximum Security Prisons where he was being held, but these turned out to be untrue. Later that month a judge set 31 May 2011 as the date for deciding whether to re-open the trial against al Mustapha. The case was reopened in July 2011. In the first two weeks of August, Hamza Al-Mustapha and his co-accused Lateef Sofolahan testified to their innocence of Abiola's killing. The court adjourned the case to 10 November 2011 when counsel to both parties were expected to file and adopt their written addresses. After receiving written submissions and hearing the addresses by the counsel to both parties on that date, Justice Mojisola Dada fixed the date of 30 January 2012 for delivering a judgement. The court subsequently found him guilty of the murder and he was sentenced to death by hanging.
On 12 July 2013, The Court of Appeal in Lagos has discharged and acquitted Hamza Al-Mustapha from the murder of Kudirat Abiola.The judgment overturns that of the Lagos High Court which sentenced him to death by hanging.The presiding judge accused the lower court of being “stroked to secure a conviction by all means. Therefore, Almustapha was set free.
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