Forensic evidence is not the only techniqueused in court.
There will be a search for any weapons nearby or at thelocation, CCTV will be used to follow any alibis the defendant may claim tohave and the defendant will also be investigated to see if there was any motivebehind the crime. Alibis are a source of testimonial evidenceand can be presented in court by defendants. They can provide crucial evidence tothe case, for example, saying that they were with or saw the defendant at acertain time and this can also provide a time frame for investigators to focuson.
However, a study in 2015 by Ricardo Nieuwkamp highlighted that only 1.6% ofalibis presented in court out of 191 studied, were deemed as believable. Alibisare believed to be extremely biased. Usually the alibi is a friend of theaccused or someone who knows them personally and so this type of evidence israther weak. Overall, there has been very little investigation into thereliability of alibis.
Humans have a natural bias which isknown as cognitive bias, which can be broken down into contextual bias, whensomeone is influenced by any background information they may already know, and conformationalbias, when someone us trying to interpret their findings to support what theyalready believe. This is commonly found in witness testimony, where a witnessto the event will stand in court and describe the events that took place. They shouldexplain in as much detail as possible to give the jury a clear idea of exactlywhat happened.
However, it is common for these statements to be slightlydeviated from what happened due to shock or fear. Elizabeth Loftus discovered throughthe use of psychological studies in 1974 that the different terms used when thewitness was asked questions had an effect on the response given (10). This shows howeasily a witness can be manipulated by lawyers and therefore reduces reliabilityas there is no way to judge how much psychological tricks have had an effect onthe witness.