1.1 Evidence and testing the truthfulness of a suspects account

In a suspect interview, decisions about what evidence should be disclosed to the suspect are quite important for a number of reasons. The suspect must understand what they are suspected of, and why they are suspected of it, but there are reasons why police may elect not to disclose all of the evidence that they hold.

There are three main reasons for this:

• First, the suspect needs to be able to provide their own account based on their own memory of the event. Like in a witness interview, it is important not to potentially ‘contaminate’ someone’s recollection of what happened by first presenting them with what someone else said.
• Second, allowing the suspect to provide their own account first adds weight to this account if it is found to be consistent with other evidence.
• The final reason is that it is very important to be able to test the truthfulness of a suspect’s account. This relates to something you learned about in Week 3 – the voluntary false confession. You may remember that the voluntary false confession is the type of false confession that does not arise as a result of investigative pressure. In this type of confession someone falsely, and voluntarily, claims to have committed a crime they haven’t committed. The police need to be able to screen out such false claims, and one of the ways they can do this is through the strategic use of evidence. This will be explained further later.

When a serious crime like a murder takes place, there might be some evidence which is not disclosed to the media or witnesses, that only the suspect (along with the police) will be aware of. Take, for example, Leonard’s death. We know (because we are part of the investigation team) that Leonard was stabbed, but that would not be common knowledge. Let us assume that there has been no press coverage of the murder to date. Therefore, if someone hands themselves in at Chadborough Police Station claiming to have strangled Leonard on the Monday afternoon, we immediately know that they are not the right suspect. We know this because the information the person has provided conflicts with the other evidence we hold. We know the approximate time of death and the method of murder are both incorrect.

In suspect interviewing, investigators go through a process where they decide what information can be immediately disclosed to the suspect, and which bits of information might need to be held back.