CSI and cadaver dogs - some facts and statistics.

[jassi]

Would you consider it good police practice not to discount their alerts until proved to be false?

[Carana]

Would you consider it good police practice not to discount their alerts until proved to be false?

If dogs started wildly howling at a plane I was about to board, I would certainly hope the police would verify the aircraft for any evidence or lack thereof. However, it would be difficult to justify keeping a plane grounded forever if no corroborating evidence was found.

[slartibartfast]

I don't understand that at the moment (and I can't find your post with the chart at the moment).

From memory, I believe you were pointing out that if dog A was 80% accurate and dog B is 90& accurate, then the probability of both of them alerting correctly would be 72%. And turning that on its head, the probability of both being wrong would be 2%.

But then there is the issue of when one of them alerts accurately and the other doesn't (in a given instance). If you can't determine which one alerted correctly and which one didn't, because there's no evidence to verify it, that's a bit of a headache.

Agreed which is why I went through all possibilities.

[jassi]

If dogs started wildly howling at a plane I was about to board, I would certainly hope the police would verify the aircraft for any evidence or lack thereof. However, it would be difficult to justify keeping a plane grounded forever if no corroborating evidence was found.

Different issue there really, as in your example, police would be looking for physical evidence of a bomb, not minute traces of some sort of explosive material.

[OxfordBloo]

Would you consider it good police practice not to discount their alerts until proved to be false?

It is good police and forum practice to use the alerts as an INDICATION of the possibility of the existence of EVIDENCE.

It is poor police and forum practice to use alerts AS EVIDENCE.

[Carana]

Different issue there really, as in your example, police would be looking for physical evidence of a bomb, not minute traces of some sort of explosive material.

Yes and no, I would have thought. If a small quantity of a potentially suspicious substance were found, there would still be reason for a forensic analysis. If the analysis concluded that it was innocuous, but within the training parameters, then it would still be a case of better safe, than sorry.

[Alice Purjorick]

No comment about the NPIA and  ACPO report calling VRD dogs' alerts into question?

If you posted a link to the entire report there might be. But commenting on the Sky News precis you posted a link to is hardly worth the effort.

[G-Unit]

It is not up to people to prove they were false.

Being false can never be excluded as a possibility.

It is up to proponents to prove that they are correct in their assumptions

Both Forensics and Science start from an assumption of ignorance and require proof of any contention.

You didn't start from an assumption of ignorance though. You started with the assumption that dogs give false alerts.

If dogs do give false alerts, what does that tell us about these two dogs in particular? It tells us they may have made false alerts. In three alerts we know that something was found, so the alerts weren't false. In the case of the other alerts we don't know if they were true or false as nothing was found. It's really that simple. No need for complicated statistical analysis of probabilities. I am making no assumptions at all, so I have nothing to prove.

[Alice Purjorick]

I agree. There is a great cloud of unknowing- people glaring in ignorance and false assumptions at the same time.

It is a FACT that all scent dogs are open to substantial error
It is a FACT that a twin Eddie Keela alert has its accuracy reduced by the product of their uncertainties
It is a FACT that Eddie reacting alone adds no knowledge to the question of cadaver odour
It is a FACT that Shannon Matthews was found after being 'declared dead' by VRDs
It is a FACT that the NPIA and ACPO have severely questioned the use of VRDs including Eddie
It is a FACT that no evidence of material of cadaver origin was found in PdL
It is a FACT that cadaver origin was only indicated separately twice in PdL

Come again? The dog said Shannon Matthews was dead. You are pulling my leg of course.
Please give cite other than a link to a very short Sky News comment on what it claimed to have seen.

[Brietta]

Agreed. But we cannot tell whether alerts are valid or not in any particular case.

There is practically nothing a dog cannot be trained to do and their skills are remarkable.   

The particular case of Eddie and Keela working in Praia da Luz involved their deployment ... doing what they do ... indicating interest in particular areas ... the forensics harvested from those areas to be sent off for analysis ... which proved inconclusive.

That an entire belief system has been built around that proves only that the misrepresentation of the significance or not of the dogs has been overtaken by the desire to implicate the McCanns in guilt all based on ignorance of the actual significance of the work of the dogs.

[John]

You do not know that. It is a belief that you have. You have no proof that either Eddie alerted to a scent or that that scent was cadaver scent.

Please specify exactly which of his many alerts you claiming to be definitely an alert to cadaver odour, then we can discuss it in detail.

You're right of course, I should have said the evidence suggests Eddie correctly identified cadaver scent given the origins of the furniture.

I have no intention of getting into any prolonged debate over the prominence and/or authenticity of Eddie's alerts safe to say he was a remarkable dog with many successes.

[Carana]

There is practically nothing a dog cannot be trained to do and their skills are remarkable.   

The particular case of Eddie and Keela working in Praia da Luz involved their deployment ... doing what they do ... indicating interest in particular areas ... the forensics harvested from those areas to be sent off for analysis ... which proved inconclusive.

That an entire belief system has been built around that proves only that the misrepresentation of the significance or not of the dogs has been overtaken by the desire to implicate the McCanns in guilt all based on ignorance of the actual significance of the work of the dogs.

I've even seen comments insisting that Eddie was responsible for securing 200 murder convictions. If anyone questions it, the reply is to "read the files" - which few actualy bother to do on the assumption that someone else must have done.

[OxfordBloo]

You're right of course, I should have said the evidence suggests Eddie correctly identified cadaver scent given the origins of the furniture.

I have no intention of getting into any prolonged debate over the prominence and/or authenticity of Eddie's alerts safe to say he was a remarkable dog with many successes.

And documented failures or uncertains.

[OxfordBloo]

Come again? The dog said Shannon Matthews was dead. You are pulling my leg of course.
Please give cite other than a link to a very short Sky News comment on what it claimed to have seen.

The NPIA report confirmed that because the investigating officers accepted the indication of cadaver odour suggested that the cadaver had been removed elsewhere that considerable police time was wasted searching areas other than where she was found.

For instance the house of her actual abductor was clean and hence the police did not search it as thoroughly as they might have if they had thought that she was still alive.

Belief without reason is dangerous.

[John]

And documented failures or uncertains.

Failures cannot be quantified so attempting a comparison is futile.