The case of cannibal Peter Bryan does not reveal systematic flaws, says the National Director for Mental Health.
Peter Bryan was sentenced on Tuesday
But Professor Louis Appleby admitted: "There are pressures in the system that still need to be tackled."
Mental health campaigners said the 2001 decision to free Bryan from a secure hospital showed "unacceptable risks" were taken within the health system.
On Tuesday Bryan, who was arrested in Walthamstow, London, was sentenced to life after admitting two manslaughters.
He was arrested last year after eating the brains of his friend, Brian Cherry, and went on to kill Richard Loudwell, 59, at Broadmoor hospital while on remand.
When he killed Mr Cherry he was staying on an open psychiatric ward at Newham General Hospital, to which he was required to return in the evenings.
In 1994 he had been detained at Rampton secure hospital for beating a shop assistant to death with a hammer, but was freed in 2001.
Professor Appleby said there was no evidence of an increase in the number of homicides committed by people with mental illnesses since care in the community became national policy.
Despite admitting to "pressures" in the system, Professor Appleby pointed to an "unprecedented" increase in the resources that have gone into mental health services in the last five years.
He said any lessons highlighted by the Bryan case would be fed into the upcoming Mental Health Bill.
A Department of Health spokeswoman said an independent inquiry would take place to investigate the care received by Bryan.
Michael Howlett, director of the Zito Trust, said the case showed mental health services were struggling to cope with dangerous patients, although he welcomed the launch of an inquiry.
He said: "We're very concerned. It's an appalling case and is another example of somebody who has been into a high security hospital, been discharged with conditions and has gone on to kill."
The trust was set up after an inquiry into the care of schizophrenic Christopher Clunis, who killed Jonathan Zito in 1992.
The chief executive of mental health charity SANE, Marjorie Wallace, said the Bryan case showed psychiatric services were being forced to take unacceptable risks with people's lives.
But Andy Bell of the Sainsbury Centre for Mental Health said claims that such cases had increased were "a myth".
He said: "Each year there are between 30 and 50 cases of homicide by a person with a mental illness."
To put this into context, he added: "There are over half a million people with a severe mental illness in the UK."
But Max Pemberton, who works as a mental health doctor within the NHS, told BBC News it was sometimes difficult to accurately assess patients.
Sometimes mistakes were made, but this did not reflect a failure of the system as a whole, he said.