3.2.1 The technique used in this criminal investigation is DNA fingerprinting (or DNA profiling).

3.2.1 The technique used in this criminal investigation is DNA fingerprinting (or DNA profiling).

3.2.2 Suspect 2 was at the crime scene.

3.2.3 The DNA banding pattern of the sample from the crime scene matches exactly the DNA banding pattern of the sample from suspect 2.

3.2.4 Two possible reasons why the suspect identified in QUESTION 3.2.2 might not be convicted if only this evidence is used are:

• The DNA sample could have been contaminated at the crime scene or during collection/analysis.
• The DNA could have been transferred indirectly (secondary transfer), meaning the suspect was not physically present at the time of the crime but their DNA was brought there by another person or object.
• The suspect could have an identical twin, whose DNA would also match.
• The evidence could have been planted at the crime scene.

3.2.5 In paternity testing, DNA fingerprinting is used to compare the DNA profiles of the child, the mother, and the alleged father. The child inherits half of its DNA from the mother and half from the father. Therefore, all DNA bands in the child's profile that do not match the mother's profile must match the alleged father's profile for paternity to be confirmed. If there are bands in the child's profile that do not match either the mother or the alleged father, then the alleged father is excluded.