The Zito Trust has submitted further evidence to the government's Mental Health Act review team, highlighting non-compliance with drug treatment in the community.
But Mind has issued a report saying poor risk management and problems with communication are the most common failures contributing to homicides by people with mental health problems.
Non-compliance with medication has been 'overstated' as a factor by health agencies and the government, according to its report.
Both charities base their claims on reviews of previously published independent homicide inquiry reports. The Zito Trust has also argued that some health authorities 'on the face of it' appear to be ignoring Department of Health guidance on setting up inquiries.
The National Confidential Inquiry into Suicide and Homicide by People with Mental Illness recently estimated that about 40 homicides are committed every year by people with mental health problems. About 30 inquiries are held each year.
But the Mind report's authors are sceptical of inquiry reports' values.
Key Issues from Homicide Inquiries. Mind, Granta House, 15-19 Broadway, Stratford, London E15 4BQ.
ZT Monitor, issue 7. Zito@netcomuk.co.uk