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The Failure3 cases4 failures

The system had the man or the information, and let it go

The moments the system had him, or had the information, and let it go.

The short answer

Why do some serial killers stay free for years?

Some killers stay free because the system fails. Police agencies keep separate files.23 A check clears the suspect.2 The person trusted to report the deaths is the killer.3 A court convicts the wrong man.421 Court records, a public inquiry’s reports and FBI statements document these failures.231623

Chain · The Failure

Four ways the system lets go

Missed chanceSeparate files · 4 agencies, 1968–1969Source: CBS San Francisco / Associated Press, “Zodiac Killer’s Cipher Solved By Amateur Codebreakers” (Dec 11, 2020). Supports: five killed between December 1968 and October 1969; the FBI San Francisco office’s statement that the case remains an ongoing investigation; Vallejo, Napa County and Solano County open case files, as well as the California Department of Justice.
Missed chanceA clean check · polygraph passed, 1984Source: Seattle Times staff, “Timeline of the Green River killer case” (The Seattle Times, Feb 18, 2011). Supports: the 1984 polygraph.
Missed chanceA trusted reporter · 215 killings undetectedSource: The Shipman Inquiry (Chairman: Dame Janet Smith DBE), Third Report, “Death Certification and the Investigation of Deaths by Coroners,” Cm 5854 (July 2003), official copy on gov.uk, Summary paras 14, 40 and 50, and para 19.1. Supports: Shipman certified the deaths of patients he had killed; a second doctor completes the confirmatory cremation certificate (Form C); the certification systems failed to detect any of his 215 victims; he avoided a coroner’s investigation in all but two; in the vast majority of cases the Form C doctors trusted him as a respected colleague.
Missed chanceThe wrong man · executed Jul 5, 1983Source: Gennady Vetrov, Komsomolskaya Pravda (Kherson edition), article on the case of Aleksandr Kravchenko (in Russian, Mar 26, 2026). Its headline, which ties the murder to another man, is not reproduced. Supports: Lena Zakotnova, 9, did not come home on Dec 22, 1978 in Shakhty; Kravchenko executed Jul 5, 1983; his sentence annulled in 1991; officially her killer has not been identified.
  • The line
  • Missed chance
Notation
The line
Time, left to right. Down the screen on a phone.
Event
A fact on the record.
Missed chance
The system had him and let him go.
The catch
The error that ended it, knocked out of line.
Open case
No one charged.
A wait
Time passes and nothing moves.
Data table
Four ways the system lets go
StepDetailNotation
Separate files4 agencies, 1968–1969Missed chance
A clean checkpolygraph passed, 1984Missed chance
A trusted reporter215 killings undetectedMissed chance
The wrong manexecuted Jul 5, 1983Missed chance

Failures

4 in this series

  1. 01

    Four police agencies each held one part of the same case

    Linkage blindness is the failure of police agencies to share what they know. Four agencies held parts of one 1968–1969 California case. It is still open.

  2. 02

    Three checks came back clean. All three men killed again.

    Gary Ridgway passed a polygraph in 1984. Police held Andrei Chikatilo that year and released him after a blood test. Harold Shipman was cleared in 1998.

  3. 03

    The person who certifies a death can also hide it

    Harold Shipman certified the deaths of patients he had killed. Since September 9, 2024, England and Wales have required an independent review of every death.

  4. 04

    When the wrong man is convicted, the real offender stays free

    Aleksandr Kravchenko was executed in 1983 and cleared in 1991. In U.S. DNA exonerations, identified actual assailants were convicted of 154 more violent crimes.

The argument

The Failure

What do these failures have in common?

The four mechanisms are separate files, a clean check, a trusted reporter and a wrong conviction. Each failure sat inside an official process: a filing system, a police check, a death certificate, a verdict. The record behind them includes a prosecutor’s court filing, a public inquiry’s reports, FBI statements and Russian trial records published from the archives.231623

What happens when agencies keep separate files?

Criminologist Steven Egger used the term linkage blindness in 1984 for police failure to share and connect information on unsolved murders.62425 Four police agencies handled four attacks in Northern California in 1968 and 1969.57891011 Five people were killed and two survived, and the offender was never caught.511

David Faraday, Betty Lou Jensen, Darlene Ferrin, Cecelia Shepard and Paul Stine were killed in four attacks in Northern California between December 1968 and October 1969.57811 A different police agency handled each attack, and the offender was never caught.57910 In 2018 a former San Francisco homicide detective who had worked the case said she was unaware of any agencies working on it collectively.11 In December 2020, the FBI said the case remained an ongoing investigation, and CBS San Francisco and the Associated Press reported open case files in Vallejo, Napa County and Solano County.8

What happens when a check comes back clean?

The suspect moves to the cleared side of the file and the case runs on. Gary Ridgway passed a polygraph in 1984 and was arrested in 2001.213 Andrei Chikatilo was held in 1984, released after a blood test, and arrested again in 1990.1416 Harold Shipman killed three more patients after a 1998 police investigation closed.315

Winifred Mellor, Joan Melia and Kathleen Grundy were killed after Greater Manchester Police closed an investigation into their doctor, Harold Shipman, on April 17, 1998, the Shipman Inquiry found.15 Gary Ridgway passed a polygraph in 1984 and was arrested on November 30, 2001.213 Andrei Chikatilo was released after a blood test appeared to rule him out, and was arrested again almost six years later.1416 A commission of experts later found that the blood group recorded for him was a technical error.1416

What happens when the reporter is the killer?

About 250 patients were killed by their doctor, Harold Shipman, the Shipman Inquiry concluded in 2005.1718 The Inquiry found that he avoided a coroner’s investigation in all but two of the 215 killings it had identified by 2003, by claiming to be in a position to certify the cause of death and persuading relatives that no autopsy was needed.318 The death and cremation certification systems failed to detect any of them, and in the vast majority of cases the second doctors who signed his cremation forms trusted him as a respected colleague.3 Independent review of every death became a legal requirement in England and Wales on September 9, 2024.1920

What happens when the wrong man is convicted?

Yelena Zakotnova, 9, was murdered in Shakhty in December 1978.421 Aleksandr Kravchenko was executed for her murder on July 5, 1983, and his conviction was annulled in 1991.421 Russia’s Supreme Court later found a second man’s conviction for the same murder unproven, and officially her killer has never been identified.41621 In the United States, the Innocence Project reports that in the first 375 DNA exonerations, from 1989 to 2020, the 165 actual perpetrators identified went on to be convicted of 154 additional violent crimes while the innocent were in prison.22

The rule

Each failure sat inside an official process: a file, a check, a certificate, a verdict.

The cases

Filed under The Failure

Questions

What is linkage blindness?

Linkage blindness is the failure of police agencies to share information on unsolved murders across jurisdiction lines and to link those murders to one offender.125 The term appears in the title of a 1984 article on serial murder by criminologist Steven Egger.624

Can a serial killer pass a polygraph?

Yes. Gary Ridgway passed a polygraph examination in 1984.213 King County prosecutors later wrote that he denied killing any of the women during the test and had already killed scores of women by then.2 He pleaded guilty to 48 murders in 2003.213

How many people did Harold Shipman kill?

The Shipman Inquiry’s final report, published on January 27, 2005, concluded that he killed about 250 patients between 1971 and 1998.1718 The National Archives’ record of the Inquiry says it positively identified 218 of them.17 He was convicted in January 2000 of 15 murders.1718

Was Aleksandr Kravchenko cleared?

Yes. Kravchenko was executed on July 5, 1983, for the murder of Yelena Zakotnova, and his conviction was annulled in 1991.421 Russia’s Supreme Court later found a second man’s conviction for the same murder unproven.416 Officially, her killer has never been identified.421

What did the FBI create to connect cases across jurisdictions?

The FBI’s Violent Criminal Apprehension Program, ViCAP, has operated since 1985.1223 The FBI describes it as the national repository for violent crimes, specifically homicides, sexual assaults, missing persons and unidentified human remains.23 Its first focus was serial killers who crossed jurisdictional boundaries.12

The record

The Failure

Sources

  1. “Serial Murder Investigation,” in L. E. Sullivan, M. S. Rosen, D. M. Schulz and M. R. Haberfeld (eds.), Encyclopedia of Law Enforcement (SAGE Publications; online edition dated Sep 15, 2007), DOI 10.4135/9781412952415.n176. Supports: linkage blindness as agencies not sharing information on unsolved murders.

  2. Norm Maleng, King County Prosecuting Attorney, “Prosecutor’s Summary of the Evidence,” State of Washington v. Gary Leon Ridgway, No. 01-1-10270-9 SEA, Superior Court of Washington for King County (November 2003), copy hosted by The Seattle Times, archived Feb 17, 2006, pp. 6, 8, 35-36, 125. Supports: he passed a polygraph in which he denied the killings; by then he had killed scores of women; his arrest on Nov 30, 2001; the forty-eight victims.

  3. The Shipman Inquiry (Chairman: Dame Janet Smith DBE), Third Report, “Death Certification and the Investigation of Deaths by Coroners,” Cm 5854 (July 2003), official copy on gov.uk, Summary paras 14, 40 and 50, and para 19.1. Supports: Shipman certified the deaths of patients he had killed; a second doctor completes the confirmatory cremation certificate (Form C); the certification systems failed to detect any of his 215 victims; he avoided a coroner’s investigation in all but two; in the vast majority of cases the Form C doctors trusted him as a respected colleague.

  4. Diletant, “The Trial: The Case of Aleksandr Kravchenko” (title translated; in Russian, Jan 27, 2018), from the Echo of Moscow radio program “Ne tak” with Alexei Kuznetsov and Sergei Buntman. Supports: Yelena Zakotnova, 9, disappeared in Shakhty on Dec 22, 1978; Kravchenko executed Jul 5, 1983; his conviction annulled in 1991; the Supreme Court excluded the count from a second man’s conviction; the murder is unsolved to this day.

  5. Ryan Ocenada and Kevin Fagan, “Zodiac Killer: Why sleuths are still obsessed with S.F.’s most notorious serial killer” (San Francisco Chronicle, Oct 22, 2023). Supports: four confirmed attacks, five killed, two survived.

  6. S. A. Egger, “A Working Definition of Serial Murder and the Reduction of Linkage Blindness,” Journal of Police Science and Administration 12(3), September 1984, pp. 348-357. Abstract record NCJ 95075, NCJRS Virtual Library (U.S. Department of Justice, Office of Justice Programs), archived copy of Nov 12, 2025. Supports: author, title, journal and date of the article.

  7. Marsha Dorgan, “Tracking the mark of the Zodiac for decades” (Napa Valley Register, Feb 18, 2007). Supports: the first two attacks: dates, places, names.

  8. CBS San Francisco / Associated Press, “Zodiac Killer’s Cipher Solved By Amateur Codebreakers” (Dec 11, 2020). Supports: five killed between December 1968 and October 1969; the FBI San Francisco office’s statement that the case remains an ongoing investigation; Vallejo, Napa County and Solano County open case files, as well as the California Department of Justice.

  9. Bay Area Television Archive, San Francisco State University, “Double Murder of Faraday & Jensen (Zodiac),” catalogue entry for KRON-TV newsfilm aired Dec 21, 1968. Supports: the Solano County Sheriff’s Department investigated the first attack.

  10. Katie Dowd, “Will DNA submitted to genealogy sites also finally catch the Zodiac Killer?” (San Francisco Chronicle, May 1, 2018; updated Feb 19, 2019), photo-gallery caption. Supports: Vallejo police received the call claiming the second attack.

  11. Anita Chabria and Ryan Sabalow, “Can DNA identify the Zodiac Killer now that it has revealed the East Area Rapist suspect?” (The Sacramento Bee, May 2, 2018, as carried by the Napa Valley Register). Supports: the speaker is a former San Francisco homicide detective who worked the case.

  12. FBI, “ViCAP Goes Online” (FBI news story, Aug 4, 2008; FBI archives, archived copy of Jan 30, 2026). Supports: ViCAP operating in 1985.

  13. Seattle Times staff, “Timeline of the Green River killer case” (The Seattle Times, Feb 18, 2011). Supports: the 1984 polygraph.

  14. Peter Conradi, “Murder on the Don” (The Moscow Times, Oct 9, 1992). Supports: the September 1984 detention; release at the beginning of 1985 because a blood and sperm group discrepancy appeared to rule him out; police discovered their error after his arrest almost six years later; final arrest in November 1990.

  15. The Shipman Inquiry (Chairman: Dame Janet Smith DBE), Second Report, “The Police Investigation of March 1998,” Cm 5853 (July 2003), official copy on gov.uk, Summary, paras 1 and 3. Supports: the Greater Manchester Police investigation ended on 17 April 1998; Shipman then killed Winifred Mellor, Joan Melia and Kathleen Grundy.

  16. Igor Nadezhdin, Lenta.ru, article on the Chikatilo trial in documents from the archives (in Russian, Nov 22, 2020; updated May 10, 2021), based on trial records and prepared with the help of the Rostov Regional Court. Its headline, which opens with a quotation of the defendant, is not reproduced. Supports: the Nov 20, 1990 arrest; the August 1991 expert commission’s finding that the 1984 blood group was a technical error; the Supreme Court panel’s ruling of Jun 30, 1993, which found the Zakotnova count unproven.

  17. The National Archives (UK), catalogue description of series JA 10, “Independent Inquiry into the issues arising from the case of Dr Harold Shipman (The Shipman Inquiry): Official Archived Website,” administrative background. Supports: the final count: about 250 killed, 218 identified; final report of Jan 27, 2005.

  18. The Irish Times, “Shipman killed 15 as a student doctor - report” (Jan 27, 2005), quoting the final report. Supports: the final estimate of about 250 patients killed between 1971 and 1998.

  19. Department of Health and Social Care, “An overview of the death certification reforms” (gov.uk guidance, updated Aug 14, 2024). Supports: every death gets independent review by a medical examiner or a coroner.

  20. The Medical Certificate of Cause of Death Regulations 2024, S.I. 2024/492, regulation 1 (legislation.gov.uk, as made). Supports: commencement on Sep 9, 2024.

  21. Gennady Vetrov, Komsomolskaya Pravda (Kherson edition), article on the case of Aleksandr Kravchenko (in Russian, Mar 26, 2026). Its headline, which ties the murder to another man, is not reproduced. Supports: Lena Zakotnova, 9, did not come home on Dec 22, 1978 in Shakhty; Kravchenko executed Jul 5, 1983; his sentence annulled in 1991; officially her killer has not been identified.

  22. Innocence Project, “DNA Exonerations in the United States (1989 – 2020),” static summary of the first 375 DNA exonerations nationwide. Supports: 165 actual assailants identified; they went on to be convicted of 154 additional violent crimes while the innocent sat behind bars.

  23. FBI, “ViCAP: Fighting Violent Crime for 25 Years” (FBI news story, Aug 26, 2010; FBI archives, archived copy of Jan 30, 2026). Supports: what ViCAP holds.

  24. Illinois Center for the Book (Illinois State Library), Illinois Authors, individual author record for Steven A. Egger (undated). Supports: Egger is a criminologist and a specialist in serial homicide.

  25. S. A. Egger, “Serial Murder: An Elusive Phenomenon” (Praeger Publishers, 1990). Abstract record NCJ 123588, NCJRS Virtual Library (U.S. Department of Justice, Office of Justice Programs), archived copy of Dec 6, 2025. Supports: the definition of linkage blindness.

Educational analysis. Adjudicated cases only. Victims named with respect.