California’s Investigator of the Year Accused of Manufacturing Evidence: Raising Questions in Hundreds of Related Cases

In 2008, Long Beach homicide detective Brian Joseph McMahon was awarded the prestigious title of Investigator of the Year by the California Homicide Investigators Association. McMahon has been involved in hundreds of cases, mainly homicides. Today he is accused of manufacturing evidence in a 1995 murder investigation, raising questions in hundreds of related cases.

In 1995, Detective McMahon and Estella Martinez were assigned to investigate the murder of Ed Weinmann, who was shot and killed in Long Beach. Paul Denham became a person of interest. However, on the day of the murder, Paul was in San Francisco and his name did not appear on any flight manifests.

But McMahon and Martinez both filed reports alleging they obtained a document from Paul’s belongings, four days after the murder, that bore the names South-West and Delta airlines, along with their phone numbers, clearly inferring that Paul contacted airlines to arrange a flight.

At the time of Paul’s 1998 trial, McMahon and Martinez had suppressed the document from the discovery file and a copy was not disclosed to the defence, neither was it introduced into trial. But that didn’t stop McMahon from testifying to its discovery and contents. Paul couldn’t explain how detectives discovered the document, and he was subsequently convicted and sentenced to life without parole.

In 2014, a copy of the document was disclosed to Paul. According to a court certified handwriting expert, a retired Long Beach Police Department (LBPD) forensic handwriting expert, it is “highly probable” that McMahon authored the document and Paul is “eliminated” as a possible author.

On August 27, 2014, LBPD initiated an investigation into this matter. (Log No. CIT2014-0143). Thereafter, the City of Long Beach Citizen Police Complaint Commission scheduled a public hearing for November 12, 2015. (CPCC 15-175.) To date, no findings have been announced.

In July 2012, McMahon retired as a LBPD detective, some 17 years following the alleged manufacture of critical evidence. His extensive career contributed to hundreds of convictions. Today, each and every one of these cases becomes tainted and potentially reversible if any material evidence was gathered/handled/introduced into trial by these detectives and influenced the conviction.

Shaun Attwood  

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