Which of the following is NOT a good source of DNA evidence?

The choice of air fresheners as not being a good source of DNA evidence is based on several factors. Primarily, DNA evidence is typically collected from items that have been in direct contact with a person's bodily fluids or cells, such as skin flakes, saliva, blood, or other biological materials. Toothbrushes, for instance, often contain saliva and other personal cellular material that can provide a good DNA sample. Similarly, face masks can carry evidence of respiratory secretions and skin cells, making them potential sources for DNA analysis.

Cellphones, too, can retain traces of DNA, particularly from frequent handling and touching, as users often leave behind skin cells or other biological material. In contrast, air fresheners are designed for the distribution of aerosolized fragrances and do not generally hold biological material from individuals. They lack direct contact with bodily fluids or cells that could yield DNA, rendering them a poor source for DNA evidence in forensic investigations.