Mutual exchange occurs when two surfaces contact; Which statement best describes it?

• A. It refers to a collaborative exchange of notes
• B. It refers to exchanging evidence between agencies
• C. There will be mutual exchange of matter when two surfaces contact each other
• D. It refers to exchanging DNA profiles

Answer: (C)

Mutual exchange describes what happens at contact: material is transferred between surfaces, leaving traces on both sides. When two surfaces touch, fibers, skin cells, dust, or other matter can move from one surface to the other, and vice versa. This mutual transfer is the basis for trace evidence and is often summarized by Locard’s principle: contact leaves a trace. The amount and type of material transferred depend on factors like the force of contact, duration, and the properties of the surfaces involved.

The other statements describe administrative actions or identification concepts rather than the physical transfer that occurs on contact, such as exchanging notes, sharing evidence between agencies, or exchanging DNA profiles as information.