POLICE OFFICERS USE OF EVIDENCE IN SUSPECT INTERVIEWS

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

Suspect is home, calls a friend (3 am) Suspect calls the friend again (4. 15 am) Victim’s Facebook page (2 days before) Party (night of the murder) 2. 30 am 1 am Before Evidence exists serra. tekin@psy. gu. se Murder No evidence After Evidence exists 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? Investigators’ planned evidence use Why? 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 whethere is any link between the suspect and the crime scene serra. tekin@psy. gu. se 23/06/2016

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

Column 1 The piece of information Column 2 What question would you ask related to this piece of information? Column 3 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 He cannot later say it was someone much money do you spend on else who had his sweater clothes? What kind of clothes do you like? What kind of clothes do you wear? What clothes did you wear to the party? 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 The piece of information Column 2 Column 3 What question would What do you want to you ask related to this achieve with your piece of information? 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 The piece of information What question would What do you want to you ask related to this achieve with your piece of information? 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 Column 3 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 nonstrategically • 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 Column 3 1 - To obtain new information about the evidence already held What do you want to achieve with your 2 - To compare the suspect’s statement with the evidence already held question? 3 - To encircle 4 - To obtain new information about the critical phase of the crime To clarify why the suspect made two phone calls very 5 To obtain new information about a theme unrelated to the crime late at night 6 - To support a hypothesis 7 - Other serra. tekin@psy. gu. se 23/06/2016

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

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

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

Results- Reasoning behind Planning 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 serra. tekin@psy. gu. se Strategic Use of Non-strategic Evidence Use of Evidence % (n) 22. 3 (47) 35. 5 (75) 43. 4 (36) 12. 8 (27) 1. 2 (1) 9. 5 (20) 6. 0 (5) 6. 6 (14) 3. 8 (8) 24. 1 (20) 10. 8 (9) 13. 3 (11) 1. 2 (1) 23/06/2016

Results- Reasoning behind Planning 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 serra. tekin@psy. gu. se Strategic Use of Non-strategic Evidence Use of Evidence % (n) 22. 3 (47) 35. 5 (75) 43. 4 (36) 12. 8 (27) 1. 2 (1) 9. 5 (20) 6. 0 (5) 6. 6 (14) 3. 8 (8) 24. 1 (20) 10. 8 (9) 13. 3 (11) 1. 2 (1) 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