Investigators have been called to the scene of a murder and find five members of the victim's family are already present at the crime scene. The victim has been stabbed and the murder weapon, a letter opener, is still lodged in his back. On the handle of the letter opener, there appear to be fingerprints dried in the victim's blood. Investigators order that all five of the family members be fingerprinted. What details of this evidence is the forensic scientist most likely examining?

The DNA of the victim's blood
The reaction of each family member
The ridge characteristics of each person's fingerprints
The size of each person's fingerprints