Courts are to be issued with the first detailed guidelines on sentencing criminals with mental health conditions and disorders.
Under the proposals, judges and magistrates would consider a series of questions when determining how much responsibility mentally-ill offenders bear for their crimes.
Did the individual's condition impair their ability to exercise appropriate judgment, make rational choices or think clearly?
The draft guidance – drawn up by the Sentencing Council – covers conditions and disorders including learning disabilities, schizophrenia, depression, post-traumatic stress, dementia and disorders resulting from drug or alcohol misuse.
It will be used in conjunction with guidelines for specific offences.
Statistics indicate that people in the criminal justice system are more likely to suffer from mental health problems than the general population, the Sentencing Council said.
It pointed to a 2017 report which suggested 23% of inmates arriving at prison had had prior contact with mental health services.
Sentencing Council member Judge Rosa Dean said: "As a society we are becoming increasingly aware of the prevalence of mental health conditions and disorders, particularly among people in the criminal justice system.
"The council believes that offenders who have a mental health condition or disorder, neurological impairment or developmental disorder should be confident that the court has the information it needs to take a consistent approach to sentencing and pass an appropriate sentence.
The proposed guidance, which would apply to offenders aged 18 and older, is not intended to change sentencing practice.
It aims to provide judges and magistrates in England and Wales with a "clear structure" to follow when dealing with individuals who have mental health conditions or disorders.
The "mere fact" that an offender has such a condition or disorder does not necessarily mean that it will have an impact on sentencing, according to the draft guidance, which is subject to consultation.
Before a custodial sentence other than one fixed by law is imposed on a mentally disordered offender, a medical report should be obtained and considered unless the court deems it unnecessary in the circumstances, the guidelines say.
They also stipulate that a court must be satisfied that treatment is available if it is considering a mental health disposal.