'Crucial evidence that I believe will lead us to Ann's killer'

Her husband, Peter, was charged with her murder in 2005. Although the case against him soon collapsed, her killer remains at large.

In the fourth part of our exclusive series about the case, Debbie Simpson - daughter of Peter, stepdaughter of Ann - writes an open letter about the way she feels the case has been handled and crucial evidence overlooked

DETECTIVE Superintendent Dave Jones was the third senior investigating officer of the Ann Heron murder to retire in the 17 years since my stepmother was killed. He went in a very public, almost stage-managed, way in December.

The headline on the story of his retirement in The Northern Echo was: We're not going to give up on Ann Heron case.

This has compelled me to adopt the same high-profile media strategy as Durham Police because I want to highlight that this cold-blooded murder is still unsolved.

I am directly related to the inquiry and have first-hand knowledge of some of the events of the day. Like the police, I have no knowledge of the identity of the perpetrator. I am emotionally linked to the case, but my intention here is to lay open the facts in a bid to get certain pieces of evidence re-examined.

I have had access to statements, which in 2005 were considered "core evidence" against Peter Heron, my father, when he was charged with Ann's murder. But this core evidence was selective and omitted certain aspects of the inquiry which, to date, have still not been fully investigated.

I believe the police investigation has failed in one of the primary duties of any murder inquiry - which is to maintain an open mind at all times.

It appears that a blinkered, narrow-minded approach has been adopted that "the husband must have done it". While this was initially a valuable line of inquiry, it should not have been the only line that the police pursued.

The primary line of inquiry should have revolved around two independent sightings, by a total of five witnesses, of a blue car, which they saw travelling at excessive speed down the driveway of Aeolian House - between Middleton St George and Darlington - where Ann and Peter lived - at 5.05pm on August 3, 1990.

Ann's estimated time of death was 5pm - a time when my father has a concrete alibi because he was at GE Stiller's transport depot, in Middleton St George, where he worked.

The witnesses said that, having sped down the drive, the car failed to stop when it reached the A67 and pulled out directly into the traffic, almost causing a collision. They described the driver as dark haired, suntanned and in his early 30s.

This description does not fit grey-haired Peter Heron, who was then 53.

Access to Aeolian House is only possible via this driveway, which provides no through road. Therefore, any vehicle driving along there must have been directly connected to the house. In 1990, the police considered the identification of this man so important that the inquiry featured prominently in all media coverage and on the BBC's Crimewatch UK programme.

They said the car was like a Ford Sierra or an Austin Montego.

Since then, though, this vital element has been dismissed as either unimportant or too difficult to pursue.

No member of the family - including Mr Heron - had or has been connected to any blue vehicle.

These witness statements were withheld by the police when they produced the core prosecution statements in the case against my father in 2005. They obviously considered them unimportant.

This vehicle and its occupant have never been traced, despite the fact that the occupant is either the perpetrator or potentially the only eye witness to the events of the day.

An article in The Northern Echo in 2004, by one of those witnesses, highlighted this sighting in detail.

I have repeatedly asked Durham Police the following questions, without reply:

* Why have these witnesses never been re-interviewed? One was a taxi-driver. The others were a family of three plus a friend returning from a day at the beach.

* Why were these witnesses never asked to assist in the creation of an artist's impression of the male driving the vehicle?

* If such a photofit was prepared, why has it never been released to the media?

* Did the vehicle leave any forensic evidence at the scene (such as tyre tracks or distance between tyres)?

The lack of success in identifying the driver of the blue car is not the only failing of the investigation.

Early in the investigation, two detective constables - Tim Lerner and Jim Loughran - told Mr Heron at Dinsdale Spa Golf Club the identity of a local man whom they believed had carried out the crime.

However, the following day, a more senior officer, by the name of Harris, visited Mr Heron and withdrew the name. Why?

In November 2005, Mr Heron was arrested, interviewed for only the second time (the first was in August 1990) and charged with murder. The charge was based on a single piece of forensic evidence, which had been verbally reported by the forensic team to the senior investigating officer.

The written report from the forensic team subsequently revealed that, although the DNA material related directly to my father, given that it was found in his own home it could have occurred naturally, and so it in no way identified him as the perpetrator of the crime.

This led to the Crown Prosecution Service discontinuing the case against Mr Heron, not due to "insufficient evidence", but due to a "lack of any form of evidence".

That is because there was no other evidence linking Mr Heron to the crime.

The police theory - that he was going to disappear into the sunset with the barmaid with whom he was having an affair - could not explain the basics: what had he done with the murder weapon?

What had happened to the clothing which, according to the pathologist, must have been extensively blood-stained? Where did he and the blue car fit in?

Like Durham Police, I have been asking questions of the Crown Prosecution Service without reply:

* Who advised that the charge against Mr Heron was appropriate?

* Why wasn't the advice of counsel sought prior to Mr Heron being charged rather than afterwards? The counsel's advice, of course, was that there was no evidence with which to proceed.

I know that people will point the finger and highlight Mr Heron's extra-marital affair at the time of the murder. But being unfaithful does not make someone a murderer.

When asked about the affair, Mr Heron did not try to hide it or deny it. He accepted the criticism that he knew would - and did indeed -come.

Since the murder, Mr Heron's life has moved on. He now has a new extended Scottish family.

When he was arrested, none of the new family members was interviewed, even though they had known him for some ten years. Surely, this was an opportunity to establish if he had slipped up in some way.

Another example of the unprofessional manner of the inquiry is that, following the arrest in 2005, several people were re-interviewed.

In one case, this comprised a chat between a witness and two detectives. The police returned later with a statement which they asked the witness to sign.

The content of this statement so concerned the witness that legal advice was sought and another formal statement was provided in the presence of a solicitor. This final statement bore no resemblance whatsoever to the one the detectives had written out to be signed.

I am not suggesting any criminal activity on the part of these officers. I am merely pointing out the standard of police work on this long-running and unsolved murder inquiry.

Instead of harassing Mr Heron with flawed forensic evidence, which did not merit exposure to formal judicial proceedings, the police should concentrate on the core issue: the blue car and its occupant.

I have always believed that Ann knew her killer. Did Durham Police fully examine the background of everyone known to the victim who fitted the description of the driver of the blue car? What steps are being taken to remedy this failing?

I firmly believe that the answer to this murder lies here. This is where Durham Police need to focus its attention.

This failing has disadvantaged and discriminated against both the victim and her families. I use the word families in plural deliberately, as the poor handling of this investigation has split a family.

Both sides do, however, have one ultimate goal: to identify the perpetrator of this crime and to have him brought to justice.

For me, that will also show once and for all that my father did not kill his wife.

To this end, I would like to pool the family's resources with those of the public and the police to identify the blue vehicle and its driver - for he will lead us to the killer.

I also feel that the time has come for some form of proper, external review to be carried out into this unsolved inquiry. Sooner or later someone in authority at Durham Police needs to be held accountable for this sorry state of affairs