凡兩個(gè)物體接觸，會(huì)產(chǎn)生轉(zhuǎn)移現(xiàn)象。即會(huì)帶走一些東西，亦會(huì)留下一些東西。

——法證之父艾德蒙·羅卡

1910 年， 法國(guó)警官艾德蒙 羅卡建立了一套黃金定律，那就是人類無(wú)論做過(guò)何種接觸，一定會(huì)留下微跡證。簡(jiǎn)而言之“凡走過(guò)必留下痕跡”。他的報(bào)告奠定了現(xiàn)代刑事鑒識(shí)科學(xué)的基石。

利用羅卡的原理，刑事鑒識(shí)人員分析 犯罪現(xiàn)場(chǎng)所發(fā)現(xiàn)的纖維，就可查出大量線索，如衣服款式、衣服售出地、甚至連織品制造商都可以查出來(lái)。藉由分析微小的纖維，微跡證鑒識(shí)員能夠確切指出嫌犯曾身處現(xiàn)場(chǎng)，進(jìn)而定罪嫌犯。

羅卡定律：凡兩個(gè)物體接觸，會(huì)產(chǎn)生轉(zhuǎn)移現(xiàn)象。即會(huì)帶走一些東西，亦會(huì)留下一些東西。

羅卡定律原述：

From Wikipedia, the free encyclopedia

The Locard exchange principle, also known as Locard’s theory, was postulated by 20th century forensic scientist Edmond Locard.

Locard was the director of the very first crime laboratory in existence, located in Lyon, France. Locard’s exchange principle states that "with contact between two items, there will be an exchange" (Thornton, 1997).

Essentially Locard’s principle is applied to crime scenes in which the perpetrator(s) of a crime comes into contact with the scene, so he will both bring something into the scene and leave with something from the scene. Every contact leaves a trace.

“Wherever he steps, whatever he touches, whatever he leaves, even unconsciously, will serve as a silent witness against him. Not only his fingerprints or his footprints, but his hair, the fibers from his clothes, the glass he breaks, the tool mark he leaves, the paint he scratches, the blood or semen he deposits or collects. All of these and more, bear mute witness against him. This is evidence that does not forget. It is not confused by the excitement of the moment. It is not absent because human witnesses are. It is factual evidence. Physical evidence cannot be wrong, it cannot perjure itself, it cannot be wholly absent. Only human failure to find it, study and understand it, can diminish its value”

—Professor Edmond Locard

簡(jiǎn)單說(shuō)來(lái)就是，只要兩個(gè)人曾經(jīng)接觸過(guò)，其中一個(gè)人身上就會(huì)有一些東西跑到另一人身上，反之亦然。 也許是塵土、血液、皮膚細(xì)胞、污泥、纖維或金屬碎屑。