A major review into deaths in police custody will be announced by Theresa May today.
The independent probe will examine the lead-up to and aftermath of fatalities and serious incidents, with a focus on the support given to bereaved families.
It will also include an investigation of issues including the use of restraints, suicides that take place within 48 hours of being detained and access to mental health facilities.
The Home Secretary will say every death in custody has the potential to "underline dramatically the relationship between the public and the police".
Last year figures showed that the number of suicides after being released from police custody reached its highest level for 10 years, with 68 people apparently taking their own lives within two days of being arrested or detained in 2013/14. The number of deaths during or after police custody, which are treated separately to suicides, fell to 11.
New statistics will be published today.
The Home Office said the review will include an evaluation of:
:: The availability of mental healthcare facilities for individuals suffering a crisis, including non-offenders, and police awareness of mental health issues.
:: Apparent suicides within two days of detention.
:: The use of restraints.
:: Incident investigation.
:: The support for families of the dead.
In a speech on the relationship between police and the public, Mrs May will say: "Police custody is the place where a number of dynamics meet. It is the place where dangerous and difficult criminals are rightly locked up, where officers and staff regularly face violent, threatening and abusive behaviour, and where the police use some of their most sensitive and coercive powers.
"But it is also a place where all too often vulnerable people, often those with mental health problems, are taken because there is no other place to go."
She will say the review will build on work which has already started, including her pledge to spend up to £15million to provide health-based alternatives for thousands of people who are held in police cells after being detained under the Mental Health Act.
Mrs May is expected to say that the experience of families of those who have died in custody and victims of other serious incidents will be at the heart of the review.
"In my time as Home Secretary, I have been struck by the pain and suffering of families still looking for answers, who have encountered not compassion and redress from the authorities, but what they feel as evasiveness and obstruction," she will say.
"I have also heard first hand the frustration of police officers and staff, whose mission it is to help people but whose training and procedures can end up causing bureaucracy and delay.
"No one - least of all police officers - wants such incidents to happen, and I know everyone involved takes steps to avoid them.
"But when such incidents do occur, every single one represents a failure - and has the potential to undermine dramatically the relationship between the public and the police."
Alex Marshall, head of the College of Policing, said: "Any death that occurs following police contact is a tragedy and it is right that every incident is scrutinised to see where these tragedies could have been prevented.
"Police officers and custody staff do a difficult job dealing with detained individuals who may be aggressive and abusive. However, policing is often seen as a service of last resort, and officers often come into contact with people in a vulnerable state.
"While we have seen significant improvement in this area over the last decade, much remains to be done to improve cross sector work. It is vital that health and social services recognise their role to help prevent the tragic loss to the families involved.
"Police forces must have established policies and procedures to ensure that deaths and successful interventions are reported, recorded, investigated and analysed to protect those in custody."