3 Forensic science evidence processes
In the UK there are three separate criminal justice systems (CJS). There is one in Northern Ireland and one in Scotland and they are devolved responsibilities of the respective governments. The third system is for England and Wales, and Dave’s attack occurred in England. Although investigative practices may differ across the three jurisdictions, forensic science and scientists play a critical role in helping investigators conduct effective investigations in all three jurisdictions. Here’s how it typically unfolds.
Teams of forensic scientists such as crime scene investigator’s (CSIs) will collect physical traces from a crime scene that may become evidence. In Dave’s case, this could mean gathering DNA samples and fingermarks from the locker room and retrieving CCTV footage from the gym’s cameras. Forensic science involves the observation, documentation, collection, analysis, and scientific interpretation of evidence during the course of an investigation (Shen & Vieira, 2016).
CSIs document the scene thoroughly: photographing the area, recording what was recovered and from where. They follow strict protocols to prevent cross-contamination and ensure evidence remains admissible in court.
Transcript: Audio 2: Crime Scene Investigator (CSI)
Items recovered from the crime scene will then be submitted to a forensic science laboratory, where they are logged. This chain of custody from the crime scene to the lab continues so that every item is tracked from the crime scene to courtroom. Ensuring that evidence is admissible in court requires that none of the objects collected are tampered with and that procedures follow due diligence (Yeboah-Ofori & Brown, 2020). Once the items are logged and stored, scientists decide which items to analyse and how.
Results from the items in the investigation can be checked against national databases.This is done by running DNA profiles through the National DNA Database (NDNAD), and fingermarks through the National Fingerprint Database (IDENT1), to identify matches with known offenders or links to other crime scenes. The UK’s NDNAD, set up in 1995, is one of the longest established and largest forensic DNA databases internationally. This can sometimes help to identify people who might be of interest in the investigation. In 2022/23, the overall DNA match rate from a crime scene profile to the NDNAD was 64%, demonstrating its continuing value as a tool in policing investigations (Home Office, 2023). Digital forensic experts may also examine phones, computers, or other devices for relevant data.
Forensic scientists and digital experts produce written reports of their findings, which are shared with investigators, prosecutors, and legal defence teams. They may also be called to give evidence in court, where they are required to remain neutral. Their role is to explain the science, not to support either side.
Transcript: Audio 3: Digital Forensic expert
It is important to note that forensic evidence rarely tells the whole story. A fingermark might place someone at a location but says nothing about why they were there or what they intended. Research has shown that the context in which fingerprint examination takes place can significantly affect expert judgement (Dror et al., 2006). Equally, digital evidence can be manipulated; material can be planted on a device, and tampered digital evidence may jeopardise its correct interpretation (Hargreaves & Patterson, 2020). The context always matters when interpreting evidence. In Dave’s case, the attacker might have used gloves and left the tablet for someone else to take, keeping only the laptop.