DNA fingerprint analysis requires a sample of DNA from a person either living or dead.
The DNA is first cut up into smaller segments with restriction enzymes. Restriction enzymes act as DNA scissors, and are specific for the segments they cut. Each restriction enzyme will cut the same piece of DNA differently.
The segments are than separated according to size using electrophoresis.
Electrophoresis separates DNA based on their size because DNA has a negative charge.
When stained, the DNA segments appear as colored bands in specific order.
These bands form a persons DNA fingerprint.
The DNA fingerprint doesn't last forever, so you have to take a picture that shows the DNA in its separated segments.