It seems, at a minimum, possible that DC Eldridge misinterpreted what he matched.
The Witness statement is here:
I am Detective Constable 196 Colin Roy ELDRIDGE I am a principal exhibits officer employed by Thames Valley Police. I am at present attached to the Major Crime Unit based at Aylesbury Police Station.
At 1000hrs on Thursday 7th AUGUST 2003 I was on duty at Long Hanborough Incident Room when I removed from secure storage the following items for examination:-
1. Exhibit SK/2 CO-PROXAMOL BOX AND STRIP OF TEN TABLETS taken from
2. Exhibit NCH/17/2 CO-PROXAMOL BLISTER PACKETS FRONT BOTTOM BELLOWS POCKET these had been removed from Dr KELLY’S coat pocket by the Pathologist
On examining both items I saw that they were identical. They were marked M & A Pharmacy Ltd and had the wording CO-PROXAMOL PL/4077/0174 written on the foil side of each of the blister type packs.
I can say that enquiries have been made with M & A PHARMACHEM who are the manufacturers of CO-PROXAMOL. The batch number shown on the tablets in our possession was checked with a view to tracing the chemist that these tablets had been purchased from. I can say that this batch number relates to approximately 1.6 million packets of tablets that will have been distributed to various chemists throughout the country.
DC Eldridge implies that he has checked the batch numbers from the two exhibits.
His description of what he did raises the potentially troubling possibility that he did no such thing.
The possibility exists that he did not match batch numbers but merely matched Product Licence Numbers.
The number "PL/4077/0174" is not a batch number; it's a Product Licence Number.
If the match was on "PL/4077/0174" then DC Eldridge has misunderstood what he has matched.
The Product Licence number is a number assigned by medicines regulators. Each product has a unique number.
The number "PL/4077/0174" would, I expect, simply mean M&A Pharmaceuticals' formulation of co-proxamol.
Whether and to what degree this seeming misinterpretation may be important depends on how much co-proxamol M&A Pharmaceuticals manufactures.
If the numbers matched by DC Eldridge were "PL/4077/0174" the possibility exists that the pills from Mrs. Kelly and from Dr. Kelly are from different batches.