Defence experts argued that Folien 1 had too little “background noise” on it for it to have been lifted from a DVD cover. Glass would retain less powder and would therefore record less background noise than a DVD’s plastic sleeve. Prosecution experts argued that how much background noise would record, can be depend on variable factors, such as the state of the substrate – e.g. how old or clean – as well as the strength and quality of the Aluminium powder used on the day.
Because we do not have the original foline, it is difficult to determine with certainty the amount of background noise.
Above is the best image we could obtain of the whole Folien 1 (without the cellophane cover)
At first sight it looks fairly clean, but what if look closer? Remember, the defence experts wanted us to believe that there are barely other prints and background noise on Folien 1.
Above is an enlargement and slightly enhanced part of Folien 1. A flurry of activity is visible in the middle bottom part. Look at the debris of prints. Maybe not good enough for identification, but they are there.
Guess what is the lift below?
It is Folien 2, lifted (without any dispute) from the glass to the right of it. This is the glass that was on the coffee table next to Inge’s body. Again, we must remember that the defence experts said that glass would not retain excess powder, that is why Folien 1 is so clean. But what now? Folien 2, which we know for sure is from a glass, is snow white? We know that it may depend on how much the glass was handled but this is reiterating our point: when it comes to background noise, it may depend on variables. How clean the substrate was. What the quality of the powder was. The dusting and lifting technique. Etc. The experts had no basis to make conclusive findings in this regard.
The experts for the prosecution argued that the Aluminium powder at the time was weaker than what is currently used by the police. The duster and lifter confirmed that the powder did not particularly adhered to backgrounds but stuck well to prints. The experts said that electrostatic build-up in a plastic sleeve can push powder away. This is why it is possible to get less powder on something like a DVD sleeve than on glass, because of this electrostatic tension. When plastic rubs against something (like clothes) it can build up and retain this tension which can push powder particles away, causing a cleaner background.
If you look at Folien 1 and 2 you need wonder, considering variables: they certainly do not seem to be lifts from the same type of surface. They are just too different. And we know Folien 2 is a glass lift. Then Folien 1 must be from something other other than glass. Maybe from a plastic sleeve?
Remember, it was the same duster and lifter handling both. Same day. Same type and batch folines. If both were lifted from glasses, why would they record so differently?
As we can see in the image below where filtering has been applied, everything is not always what it seems to be. Although the image below should not tell us much about background (as scratches can be on the cellophane cover as well) it simply tells us that Folien 1 could have told us much more. Instead the experts relied on visual observations alone and ignored things that did not suit them.
We did some tests with the Al powder the police currently uses and could find no significant difference in how it adheres to glass and plastic sleeve. Clean surfaces (of these two types surfaces) retain powder about equally. But again, in real life circumstances it can depend on many variable factors. Without us having that specific powder used on that day, and without having the actual substrates as they were on that day, we (or anybody else) cannot and should not make conclusive findings on the background noise issue.
But, what is safe to say, is that the “not enough background noise” should not favour the glass theory one bit.