Blood-type evidence is crucial because it can:

Blood-type evidence plays a significant role in forensic science, particularly in its ability to narrow down suspect possibilities. Each individual has a unique blood type that can be classified into several groups, such as A, B, AB, or O, along with Rh factor (positive or negative). When blood-type evidence is found at a crime scene, it can help investigators determine which individuals may potentially be involved based on their blood types.

This information is useful because if a suspect's blood type does not match the blood type found at the scene, they can likely be ruled out as a potential perpetrator. Conversely, if their blood type matches, they remain a candidate for further investigation. This process helps streamline the investigation by eliminating individuals who cannot be linked to the crime based on blood-type compatibility.

While blood type can assist in excluding some individuals, it does not offer the same level of specificity as DNA matching, which is more definitive. Blood evidence does not confirm the identity of the victim or provide a precise time of death either. In summary, the strength of blood-type evidence lies primarily in its ability to narrow down a list of suspects, thereby focusing investigative efforts.