Police officers’ use of evidence in suspect interviews: How and Why? Serra tekin, PÄr Anders Granhag & Leif A. StrÖmwall serra.tekin@psy.gu.se 23/06/2016

Imagine… A woman has been murdered The crime took place between 1 am and 2.30 am on a Sunday morning A suspect was arrested serra.tekin@psy.gu.se 23/06/2016

Victim’s Facebook page Suspect is home, calls a friend (3 am) Victim’s Facebook page (2 days before) Suspect calls the friend again (4.15 am) Party (night of the murder) 1 am 2.30 am Before Murder After Evidence exists No evidence Evidence exists serra.tekin@psy.gu.se 23/06/2016

The investigators possess evidence pertaining to several (less critical) phases of the crime, but lack information about the most critical phase serra.tekin@psy.gu.se 23/06/2016

How should the suspect be interviewed to elicit information about the critical phase (between 1 am and 2.30 am)?

Research questions How do investigators use the available evidence when their aim is to elicit admissions about the critical phase? Why? Investigators’ planned evidence use Investigators’ reasoning behind their planning serra.tekin@psy.gu.se 23/06/2016

Method: Survey N = 69 police officers (fictitious case + questions regarding planning) The Netherlands (n = 50, 72%) Norway (n = 15, 22%) U. K. (n = 4, 6%) Age: 24 to 59 (Myears = 42.1, SD = 9.3) Experience: 1 to 28 years (M = 9.9, SD = 6.8) 66% received training on suspect interviewing serra.tekin@psy.gu.se 23/06/2016

Case & objective Objective: You are now asked to plan an interview with the suspect based on the case information. In this interview, your objective is to collect new information from the suspect. Specifically, we would like you to focus on eliciting new information to be able to infer whether there is any link between the suspect and the crime scene serra.tekin@psy.gu.se 23/06/2016

The piece of information Column 1 Column 2 Column 3 The piece of information   What question would you ask related to this piece of information? What do you want to achieve with your question? serra.tekin@psy.gu.se 23/06/2016

The piece of information Column 1 Column 2 Column 3 The piece of information   What question would you ask related to this piece of information? What do you want to achieve with your question? The victim was killed with several blows to the head How did you kill Linda? Figure out how the crime has taken place and more importantly why. Suspect’s route leaving party The suspect was on the phone at night What is your calling behaviour? To check whether he calls more often at night The red sweater Where do you spend your income on? How much money do you spend on your hobbies? How much money do you spend on clothes? What kind of clothes do you like? What kind of clothes do you wear? What clothes did you wear to the party? He cannot later say it was someone else who had his sweater CCTV footage Suspect’s browser history serra.tekin@psy.gu.se 23/06/2016

Coding- Planned use of evidence Strategic (obtaining the suspect’s statement before disclosing a particular piece of evidence) Column 1 Column 2 Column 3 The piece of information   What question would you ask related to this piece of information? What do you want to achieve with your question? Eyewitness statement indicating that the suspect was drunk at the party Can you tell me what you have drank at the party? serra.tekin@psy.gu.se 23/06/2016

Coding- Planned use of evidence Non-strategic (disclosing the evidence to the suspect before posing questions about it) Column 1 Column 2 Column 3 The piece of information   What question would you ask related to this piece of information? What do you want to achieve with your question? Eyewitness statement indicating that the suspect was drunk at the party We have eyewitness evidence indicating that you were drunk at the party. Tell me what you have drank serra.tekin@psy.gu.se 23/06/2016

Results- Planned Use of Evidence 283 questions were formulated (+ 37 were in the ‘other’ category) Strategic use: 70% of the time Non-strategic use: 30% of the time The investigators planned to use the evidence strategically (M = 2.87, SD = 2.42) more often than non-strategically (M = 1.23, SD = 1.67) . serra.tekin@psy.gu.se 23/06/2016

Results- Planned Use of Evidence N = 69 investigators, 3 groups of investigators 31 (44.9%): planned to disclose all pieces strategically 12 (17.4%): planned to disclose all pieces non- strategically 26 (37.7%): planned to disclose some pieces strategically, others non-strategically serra.tekin@psy.gu.se 23/06/2016

Coding- Reasoning behind Planning 7 categories 1- To obtain new information about the evidence already held 2- To compare the suspect’s statement with the evidence already held 3- To encircle 4- To obtain new information about the critical phase of the crime 5 To obtain new information about a theme unrelated to the crime 6- To support a hypothesis 7- Other Column 3 What do you want to achieve with your question? To clarify why the suspect made two phone calls very late at night serra.tekin@psy.gu.se 23/06/2016

Coding- Reasoning behind Planning 7 categories 1- To obtain new information about the evidence already held 2- To compare the suspect’s statement with the evidence already held 3- To encircle 4- To obtain new information about the critical phase of the crime 5- To obtain new information about a theme unrelated to the crime 6- To support a hypothesis 7- Other Column 3 What do you want to achieve with your question? To compare the suspect’s statement about the chain of events with the witness statements serra.tekin@psy.gu.se 23/06/2016

Coding- Reasoning behind Planning 7 categories 1- To obtain new information about the evidence already held 2- To compare the suspect’s statement with the evidence already held 3- To encircle 4- To obtain new information about the critical phase of the crime 5-To obtain new information about a theme unrelated to the crime 6-To support a hypothesis 7-Other Column 3 What do you want to achieve with your question? To establish who else uses the phone serra.tekin@psy.gu.se 23/06/2016

Coding- Reasoning behind Planning 7 categories 1- To obtain new information about the evidence already held 2- To compare the suspect’s statement with the evidence already held 3- To encircle 4- To obtain new information about the critical phase of the crime 5- To obtain new information about a theme unrelated to the crime 6- To support a hypothesis 7- Other Column 3 What do you want to achieve with your question? To find out the suspect’s route from the party to his home serra.tekin@psy.gu.se 23/06/2016

Results- Reasoning behind Planning    Categories  Strategic Use of Evidence % (n)  Non-strategic Use of Evidence 1. To obtain new information about the evidence already held 22.3 (47) 43.4 (36) 2. To compare the suspect’s statement with the evidence already held 35.5 (75) 13.3 (11) 3. To encircle 12.8 (27) 1.2 (1) 4. To obtain new information about the critical phase of the crime 9.5 (20) 6.0 (5) 5. To obtain new information about a theme unrelated to the crime 6. To support a hypothesis 6.6 (14) 24.1 (20) 7. Other 3.8 (8) 10.8 (9) serra.tekin@psy.gu.se 23/06/2016

Results- Reasoning behind Planning    Categories  Strategic Use of Evidence % (n)  Non-strategic Use of Evidence 1. To obtain new information about the evidence already held 22.3 (47) 43.4 (36) 2.  To compare the suspect’s statement with the evidence already held 35.5 (75) 13.3 (11) 3. To encircle 12.8 (27) 1.2 (1) 4. To obtain new information about the critical phase of the crime 9.5 (20) 6.0 (5) 5. To obtain new information about a theme unrelated to the crime 6. To support a hypothesis 6.6 (14) 24.1 (20) 7. Other 3.8 (8) 10.8 (9) serra.tekin@psy.gu.se 23/06/2016

The notion of… …using the known information (pertaining to less critical phases) as a vehicle to elicit admissions about a phase for which information is lacking IS RATHER NOVEL serra.tekin@psy.gu.se 23/06/2016