THEORETICAL ANALYSIS OF THE BIOLOGICAL BASIS FOR SERIAL KILLERS’ COOLING-OFF PERIODS by HARRIET FFION LYNETTE DILLY A THESIS Presented to the Department of Biology and the Robert D. Clark Honors College in partial fulfillment of the requirements for the degree of Bachelor of Science June 2021 An Abstract of the Thesis of Harriet F. L. Dilly for the degree of Bachelor of Science in the Department of Biology to be taken June 2021. Title: Theoretical Analysis of the Biological Basis for Serial Killers’ Cooling-Off Periods Approved: ___ Nicole Dudukovic, Ph.D._________________ Primary Thesis Advisor Although serial killers have been meticulously studied, there is still much to be learned about particular behaviors exhibited by these offenders. In particular, minimal research exists on the phenomena of serial killers’ cooling-off periods. Most definitions of serial killers mention the temporal separation between crimes that distinguish them from other kinds of multi-victim murders; however, due to a lack of empirical research it has been difficult to determine the function or cause of cooling-off periods. There has been a recent uptick in research published on cooling-off periods as interest in the neural activity of serial-killers has increased and as brain scanning technology has become more accessible. However, due to the inherent limitations of brain scans, there exists demand for an alternative method to understanding the function and cause of cooling-off periods. First proposed by M.V Simkin and V.P. Roychowdhury in 2014, it is hypothesized that cooling-off periods may be compared to the refractory periods of neurons during the propagation of action potentials. This approach is considered analogical and will remain as such until definitive evidence is produced showing a biological linkage between the two phenomena. This thesis applied this hypothesis to ten cases of prolific serial killers and looked to verify trends seen in previous research on cooling-off periods. It was concluded that the previous observed patterns were not applicable across all killers and the connection between refractory periods and cooling- off periods will remain speculative until further empirical research is done. ii Acknowledgements While countless people deserve acknowledgements, I will keep my recognitions brief. I would like to thank my primary thesis advisor, Professor Nicole Dudukovic, for her invaluable guidance and belief in this project. Without her, this thesis would have remained just another crazy idea. I would like to thank my second reader, Professor Nathan Tublitz, for pushing me to be more critical and believe in my ideas. I hope to repay his efforts someday with a batch of chocolate chip cookies. I would like to thank my third reader, Professor Melynda Casement, for taking a chance on this project and agreeing to be a part of my committee. I hope to have the pleasure of meeting her in person someday. I would like to thank my parents, Stephen Dilly & Lynette Mullens, for their unwavering support of my academic pursuits. I would like to thank my friends and teammates for being my support system throughout this process. Finally, I would like to thank my dog Bert, whose company during late night work sessions made this thesis possible. ••• ••• —•• ——• —— iii Table of Contents Introduction 1 Background 3 Why Someone Becomes a Serial Killer 3 Existing Research of Brain Function of Serial Killers 5 Existing Research on Cooling-Off Periods 10 Methods 16 Case Studies 18 Case Study I: Joseph James DeAngelo (aka EARONS, Golden State Killer) 18 Case Study II: Jeffrey Lionel Dahmer (aka Milwaukee Cannibal) 23 Case Study III: John Wayne Gacy (aka Killer Clown) 26 Case Study IV: Theodore “Ted” Robert Bundy 30 Case Study V: Richard Leyva Muñoz Ramírez (aka The Night Stalker) 35 Case Study VI: Edmund Emil Kemper III (aka Co-ed Killer) 37 Case Study VII: Dennis Lynn Rader (aka BTK Killer) 42 Case Study VIII: David Richard Berkowitz (aka Son of Sam) 44 Case Study IX: Randall Woodfield (aka I-5 Killer, I-5 Bandit) 47 Case Study X: Gary Leon Ridgway (aka Green River Killer) 50 Discussion 55 Methodological Limitations 60 Conclusion 62 Bibliography 64 iv List of Figures Image 1: Composite of brain regions exhibiting reduced grey matter in murderers as compared to other violent offenders. Reprinted with permission from Sajous-Turner (2019). 7 Image 2: DeAngelo's mugshot after arrest on April 24, 2018. 18 Figure 1: Distribution of DeAngelo's murders over time. The shortest time elapsed between crimes was 74 days, while the longest was 1742 days. 20 Figure 2: Distribution of DeAngelo's murders without the 1986 outlier. Average time between crimes was 357.7 days (SD. 338.2). The longest elapsed time between crimes was 875 days. 21 Figure 3: Distribution of DeAngelo's murders and sexual assaults without the 1986 outlier. Average time between crimes was 38.3 days (SD = 55.5). The shortest elapsed time was 20.5 hours, while the longest elapsed time was 281 days. 22 Image 3: Dahmer's mugshot after arrest on July 22, 1991 23 Figure 4: Distribution of Dahmer's murders without 1978 outlier. Average time between crimes was 47.38 days (SD = 46.18). The shortest elapsed time between crimes was 3 days, while the longest was 147 days. 26 Image 4: Gacy's mugshot after arrest on December 22, 1978. 26 Figure 5: Distribution of Gacy's murders over time. The shortest time elapsed between crimes was 0 days, while the longest was 1295 days. 29 Figure 6: Distribution of Gacy's murders without 1972 and 1975 outliers. Average time between crimes was 40.79 days (SD = 40.04). The shortest elapsed time between crimes was 0 days, while the longest was 134 days. 30 Image 5: Bundy’s mugshot after conviction on August 1st, 1979. 30 Figure 7: Distribution of Bundy's murders over time. The shortest time elapsed between crimes was 0 days, while the longest was 932 days. 33 Figure 8: Distribution of Bundy's murders before 1975 arrest. Average time between crimes was 32 days (SD = 22.8). The shortest elapsed time was 0 days, while the longest was 80 days. 34 Image 6: Ramirez in 2007. 35 Figure 9: Distribution of Ramírez's murders without 1984 outlier. Average time between crimes was 17.11 days (SD = 18.79). The shortest elapsed time between crimes was 0 days, while the longest was 49 days. 37 Image 7: Kemper's mugshot in 1973. 37 Figure 10: Distribution of Kemper's murders over time. The longest interval between crimes was 2,808 days, while the shortest was 75 days. 40 v Figure 11: Distribution of Kemper's murders without 1964 outlier. Average time elapsed between crimes was 87.75 days (SD = 46.5). The longest interval was 132 days, while the shortest was 28 days. 41 Image 8: Rader's mugshot after arrest on February 25, 2005. 42 Figure 12: Distribution of Rader's murders over time. The longest elapsed time was 2697 days, while the shortest was 79 days. 43 Image 9: Berkowitz's mugshot after arrest on August 11, 1977. 44 Figure 13: Distribution of Berkowitz's murders over time. The longest elapsed time was 185 days, while the shortest was 37 days. 46 Image 10: Woodfield's mugshot on March 9th, 1981. 47 Figure 14: Distribution of Woodfield's murders over time. The longest elapsed time was 52 days, while the shortest was 12 days. 49 Image 11: Ridgway's mugshot after arrest on November 30, 2001. 50 Figure 15: Distribution of Ridgway's murders over time. The longest elapsed time was 1122 days, while the shortest was 0 days. 53 Figure 16: Distribution of Ridgway's murders without five outliers. Average time elapsed between crimes was 12.85 days (SD 12.75). The longest interval was 45 days, while the shortest was 0 days. 54 Figure 17: Distribution of SD of cooling-off periods. 58 vi List of Tables Table 1: DeAngelo's murders between Sept. 11, 1975 and May 4, 1986. The average elapsed time between murders was 555.42 days (SD = 607.5 days). 19 Table 2: Dahmer's murders between June 7, 1978 and July 19, 1991. The average elapsed time between murders was 299.44 days (SD = 833.06). 24 Table 3: Gacy's murders between Jan. 3, 1972 and Dec. 11, 1978. The average elapsed time between murders was 97.46 days (SD = 250.96). 27 Table 4: Bundy's murders between Feb. 1, 1974 and Feb. 9, 1978. The average elapsed time between murders was 77.32 days (SD = 208.15). 32 Table 5: Ramierez's murders between Jun. 28, 1984 and Aug. 18, 1985. The average elapsed time between murders was 41.6 days (SD = 79.44). 36 Table 6: Kemper's murders between Aug. 27, 1964 and Apr. 21, 1973. The average elapsed time between murders was 631.8 days (SD = 1217.2). 39 Table 7: Rader's murders between Jan. 15, 1974 and Jan. 12, 1991. The average elapsed time between murders was 1034.3 days (SD = 984.2 days). 43 Table 8: Berkowitz’s murders between Jul. 29, 1976 and Jul. 31, 1977. The average elapsed time between murders was 91.75 days (SD = 69.9). 45 Table 9: Woodfield’s murders between Oct. 9, 1980 and Feb. 15, 1981. The average elapsed time between murders was 32.25 days (SD. = 21.17). 48 Table 10: Ridgway’s murders between Jul. 8, 1982 and Mar. 5, 1990. The average elapsed time between murders was 63.57 days (SD = 215.53). 51 Table 11: Summary of the average length of cooling-off periods in the ten case studies.