The BBC Scotland programme Britain's Private War sent a list of questions to G4S, to which a spokesman for the private security contractor responded.
•Both Paul McGuigan's and Danny Fitzsimons parents claim the company was at fault by not adequately checking the criminal and psychological background of Fitzsimons before employing him in Iraq. Do you agree with this statement?
G4S spokesman: "This was a tragic case and our thoughts remain with the families of both Paul McGuigan and Darren Hoare, who were valued and highly respected employees of the company, and who continue to be sadly missed by their families, colleagues and friends alike.
"We confirmed publicly on 15 September 2009 that, in this particular case, although there was evidence that Mr Fitzsimons falsified and apparently withheld material information during the recruitment process his screening was not completed in line with the company's procedures.
"Our screening processes should have been better implemented in this situation but it is a matter of speculation what role, if any, this may have played in the incident."
•Do you believe G4S-ArmorGroup adequately vetted Danny Fitzsimons before employing him? Can you please outline the interview process and explain exactly what checks were done by the company prior to taking on Fitzsimons?
G4S spokesman: "See answer above.
"We received two separate medical documents which certified that Mr Fitzsimons was fit to work in Iraq. It subsequently came to light that the most recent of those documents was forged - we believe, falsified by Mr Fitzsimons.
"Mr Fitzsimons was also found to be mentally fit to stand trial by a court of law and before he was convicted of the killing of Paul and Darren."
•Do you believe that there were failings by ArmorGroup that could warrant a criminal investigation, and would you co-operate with a criminal investigation should one be forthcoming?
G4S spokesman: "It is not for G4S to comment on the appropriateness of any criminal investigation. The company has fully and unconditionally cooperated with enquiries from the police and authorities in both the UK and Iraq at all times.
"Mr Fitzsimons was found solely responsible for the killing by a court of law.
"The police have stated in open court that in their view and that of the CPS (Crown Prosecution Service) there is no corporate manslaughter investigation worth conducting."
•When did the company first become aware of the emails and why were the warnings not acted upon?
G4S spokesman: "We are aware of this allegation but following an internal IT investigation it is clear that no such emails were received by any member of our HR department."
•What steps have the company taken to ensure that an incident such as happened in the Fitzsimons case does not happen again?
G4S spokesman: "Following the incident, we immediately installed an additional team of screening professionals who checked through every single employment file to make sure the records were up-to-date and contained everything required to confirm suitability for employment with the company and deployment to Iraq and other hostile environments.
"No-one needed to be dismissed from the company as a result of failing this process.
"The screening and vetting is now carried out by G4S Screening & Vetting which works to BS 7858 and is independently audited by the National Security Inspectorate.
"We also introduced new processes to ensure that these standards are applied strictly to future recruitment.
"The most important of these was to introduce in-house medical and psychological testing prior to deployment - although previously we asked for medical and psychological confirmation from potential employees' doctors the feedback was not consistent so this new testing regime is based on in-depth knowledge of the environment the individuals will be deployed into."
•In terms of regulation of the industry, does the company believe that the industry is adequately regulated? Are there any changes the company would like to see introduced?
G4S spokesman: "As outlined in my previous response, the legal and regulatory framework within which British PSCs (private security companies) operate already includes a number of components. The fact that Mr Fitzsimons was tried, found guilty and imprisoned for his crimes proves that if employees of PSCs break the law there is a high level of accountability even in complex environments.
"G4S has been at the leading edge of regulation since 2004, when we first called for the government to regulate the industry.
"Having been one of the drivers behind and initial signatories of the International Code of Conduct for Private Security Service Providers, we have been heavily involved in turning those principles into a set of standards against which companies can be accredited and sanctioned if they do not live up to these standards.
"We were also the driver behind the development of the new Security in Complex Environments Group (SCEG), which is the UK government's chosen partner for introducing the regulation of UK private security companies working overseas."
For clarification, we also asked the company the supplementary question:
•When did the company first become aware of the emails and did anyone else - outside of the company's HR department - become aware of them?
A G4S spokesman said: "I'm sorry I can't track down the relevant individual so I am afraid we can not comment further on when we received the emails."