There's something wrong with the fingerprints

Generally, fingerprints will not be left, but it will leave a smell.

When people touch objects, they leave fingerprints because people have grease on their hands. Fingerprint powder shows the shape of grease.

The two substances are in contact with each other, but there is no trace when there is no oil secretion.

Because oil will be lost in the natural state, it is difficult to trace objects that people come into contact with other things.

Not only consumption, but more importantly, it has penetrated into it.