Detectives investigating the deliberate contamination of products at Stepping Hill Hospital say they continue to make good progress in their search for the poisoner.
A team of detectives from the Greater Manchester force's Major Incident Team are investigating the contamination of various products with insulin between 1 June 2011 and 15 July 2011.
Twenty-two people were subsequently poisoned by the contaminated products, seven of whom have since died. They are Tracey Arden, 44, Arnold Lancaster, 71, Derek Weaver, 83, William Dickson (known as Bill), 82, Linda McDonagh, 60, John Beeley (known as Jack, 73 and Beryl Hope, 70.
Detectives are investigating, reviewing and analysing each of the hundreds of interactions all 22 patients had with a member of staff or visitor during their time at Stepping Hill.
This process also has to be completed for the 20 other patients who suffered hypoglycaemic episodes but who, following investigation and expert medical analysis, are not believed to be victims of poisoning.
GMP continues to work closely with staff at Stepping Hill Hospital, other medical experts and the CPS as part of the ongoing investigation.
Ultimately a file of evidence will be prepared that will be heard before a jury and/or coroner, whose job it will be to rule on the causes of death and how, if at all, the insulin from contaminated products contributed to their death.
In the 12 months since the investigation began, GMP has:
Generated more than 3,800 pieces of work.
Taken more than 650 statements.
Spoken to 800 members of staff.
Gathered almost 3,000 exhibits.
Generated more than 9,800 documents.
Obtained information relating to more than 2,300 people including patients, hospital staff and visitors.
Experts have been carrying out specialist medical tests that include:
Comprehensive examination of drugs present in the body after death.
Comprehensive examination of drugs present in the patient while being treated (where available).
Examination of natural disease present after death.
An understanding of clinical treatment and symptoms presented by the patient whilst in hospital.
Clinical reviews of the patient's general state of health surrounding admission to hospital and any relevant medical history.
An understanding of the types of insulin used to poison the victims.
Measurement of the levels of insulin administered.
Detective Superintendent Simon Barraclough, said: "We have set ourselves the task of understanding and proving how each person was poisoned, how and if this caused or contributed to their deaths and obviously who is responsible.
"To that end we are making good progress, but it won't be until the very end of the criminal or coronial process that these questions will be properly answered.
"Ultimately our aim is to ensure justice for all victims.
"The sheer size and complexity of this investigation is reflected in the number of inquiries that we have done, those still to do and the specialism surrounding all medical evidence and the invaluable and necessary involvement of the various exerts who are supporting and assisting us.
"I want to take the opportunity to thank all the staff at Stepping Hill. I know the past 12 months have been an extremely difficult and challenging time for them but they have offered us their full and unwavering support throughout.
"It is important to note that we continue to work with them regarding the safeguarding of patients and since we were alerted back in July last year no other products have been contaminated."
Judith Morris director of nursing and midwifery at Stockport NHS Foundation trust said: "Our staff are determined that this criminal and malicious event does not overshadow the hospital's long-standing record of good care and we are grateful for the outstanding support for our community.
"The police investigation may be ongoing, but we have always been clear that the deplorable act of deliberate contamination does not reflect on the good care provided by our skilled and dedicated staff."