I have read True Lineages but I did not find where the magic leaves traces.
On the subject only or on the enviroment where the spell was cast, too?
E.g. I create a knife and cut a branch of a bush with it. The spell expires, the knife disappears. Has this magic any trace somewhere?
If someone is under the effect of a spell and moves does he leave magic traces on his route?
page 71 in HoH:TL
The Intellego Vim Guidelines on page 158 in the core rules give extra detail.
Seems likely that somone under the effects of a spell , even if moving , would leave a magical residue.
But this would deteriorate very quickly unless the spell was of very high magnitude.
Odor of Lingering Magic on page 75 of True Lineages may be helpful to read also.
Maybe because of language problems but this is not an answer to all of my questions.
It means IMO the quesitor first want to localize the target of the spell. So if someone say to her here was cast the "guilty" spell or this was the target of the spell she will go there to investigate it.
Other "subjects" will be the accused person(s) with Mentem magic if they do not admit the charge.
If this target is a body she will observe it. - This is ok, I thought of course the target has traces on itself.
The "suspected area" can be also the mentioned body I think it does not mean "enviroment" here.
The other references you gave have nothing to do in this question. 
Why do you think this?
The Phantom Gift page 157 (ArM 05)
Regular people and animals can sense magic in this manner , by proximity , sight alone is not a determining factor.
This leads me to see magic as contaminating the environment in some manner.
Magic must leave traces in an area or environment , because this is the basis of some Arcane Connections (page 84).
The InVi guidelines allow for detecting Magical items , Magical Creatures and Raw Vis also.
It describes how residues of magic decline , as does the section in True Lineages.
Vis will leave traces in the environment surrounding where it can be found.
(it can be extracted from a Magical Aura after all , and an Aura is detectable)
Most spells are based on giving the target a Magical sense to detect either a Magical Aura or traces of magic.
Odor of Lingering Magic is just one type of InVi spell to detect traces of magic.
Sight of the Sigil is another.
You can make an Acute Sense Roll (page 71 , HoH:TL) , if you have that ability.
Magic Residue must be present in the environment , by default , to be detectable by magical senses.
I understand it already. The rules do not clarify this and you must use your logic to find out some house rule. Also I have some logic but I was curious of the official rules.
Anyhow, thanks for your efforts finding an answer!
Btw I would vote enviroment + target but I think it is better if things under the effect of magic do not leave traces.