[pxl_rip]

The problem is that i noticed for the three legit orders is that on the proof of delivery on dhl (.co.jp domain ships only with dhl) there is the sign of my doorman. Where I live all of the shippings are received by him.
Is this a problem for a DNA method? I don't want to put him in trouble.

Unless you're well-acquainted with the other person (In your case, the doorman), It's not good practice to Involve others with your SE.

It may Impact on him as well as your claim, for the fact that he's not part of your social engineering activities.

In reality I think all of the carriers write the doorman sign by themselves.
I'm friend of the doorman but I don't want to run risks.
Do you think DNA is suitable for this situation or I have to go with wrong item for example? Is this method working for two objects? (a watch and a camera lens)

You have to esxcuse me for all of this bothering but I want to minimize risks as much as possible.