In case of robbery, the police visit the robbery scene and collect some samples like foot print or any item suspected to have been touched by the robber. The sample is then taken to laboratory for DNA analysis. Does that mean whatever we hold or touch, our DNA sticks or drops on it?
Yes, we leave DNA on everything we come in contact with. Even simply standing, we shed skin cells and hair (although only the follicle has DNA) etc. DNA may also be transferred from clothes to clothes.
You might be interested to read this article :) http://www.forensicsciencesimplified.org/dna/how.html
Yes, and as DNA technology becomes more sensitive, there is the unfortunate effect where it's very easy to detect the DNA of a person who hasn't personally been in the location, or was a long time ago. The amplification of DNA is incredibly efficient now, theoretically needing a single cell