The Impossible Puzzle: Gianrico Pierucci’s Three-Year Quest to Uncover America’s Most Notorious Serial Killer


By Kaiyo Funaki

For three years, Gianrico Pierucci was tasked with the most daunting job any homicide inspector could come across–catching the Zodiac Killer.

The 57-year old City College administration of justice professor and alumni of the college joined the SFPD in 1987, working his way up the ranks across three decades of public service. 

His promotion to homicide inspector in 2007 eventually led to an expansion of responsibilities, and by 2013, he had inherited over 200 unsolved cases as part of the cold case unit. 

Pierucci worked diligently to continue the work of the previous inspectors and strived to build momentum on cases that had yet to be closed.

Gianrico Pierucci reminisces his tenure as a homicide inspector. San Francisco, CA. Oct. 25, 2020. Photo by Melvin Wong/The Guardsman.


Though he invested an equal amount of time and effort into each case, only one had the infamy to be popularized in pop culture and spun into a feature-length film.

Described by Pierucci as the “Jack the Ripper of the United States,” the Zodiac Killer left a  chilling string of murders that has left professional and amateur sleuths befuddled for the last 50 years.

The Zodiac Killer terrorized Northern California in the late 1960s, murdering at least five people and severely injuring two others. 

He frequently tormented SFPD and local newspapers with his cryptic letters and ciphers, citing his intimate knowledge of the crime scene and willingness to commit more acts of violence should the newspapers refuse to publish his letters.

He signed off each letter with his signature crosshair-like symbol, a haunting emblem that only added to the Zodiac’s notoriety. 

In 1969, he murdered taxi driver Paul Stine in the Presidio Heights district of San Francisco and claimed responsibility for his crime by sending the San Francisco Chronicle a portion of Stine’s bloodied shirt.

Despite having thousands of suspects, the SFPD has never convicted anyone, and the case remains unsolved to this day.

Due to its open nature, Pierucci declined to discuss specificities to avoid revealing any classified information that might compromise the progress of the ongoing investigation.

However, he did recall some of the challenges of one of the most mysterious serial killers in recent history.

When Pierucci and his coworkers first began diving into the Zodiac in 2014, they had to sift through 26 boxes of evidence.

He often found himself going down the rabbit hole, staying late at the office doing research.

“It’s all glory on TV, but a lot of times, you can’t even see straight with your glasses on. You’re reading so much stuff; there’s newspaper articles from way back when, there’s letters people wrote… If there’s one thing about cold cases, you have to go back and see what everyone else did.”

They eventually added to that stack of boxes, compiling 16 more binders of information.

Pierucci routinely received tips about possible suspects, and despite the low chances of legitimacy, never once took a possible lead for granted.

A close up of the wanted poster is seen here as Gianrico Pierucci files through his notes. San Francisco, CA. Oct. 25, 2020. Photo by Melvin Wong/The Guardsman.

“You can’t cut corners on investigations like this…but there were so many different people that call in about so many different suspects, it begins to get kind of crazy,” he said.

The reputation of the case and the publicity it received only complicated matters, as Pierucci often dealt with people who obtained a vast amount of information from online resources.

Even though he occasionally dealt with bouts of frustration, he “never once wanted to give up,” and his passion for the job kept him motivated through every dead end.

“Investigations is like a puzzle; you’re going through forensics, reading through the reports, looking at the witness information, and you’re trying to figure out how it all comes together,” Pierucci said. 

“You don’t always have the pieces, but the more you do, the more pieces you might be able to find to put in there, and it always fascinated me to go out and look for the pieces.”

At one point, Pierucci and his peers even believed to have found their mystery man, but the lab analysis of their evidence came back negative.

After working 30 years for the SFPD, Pierucci retired and relinquished his duties as a homicide inspector.

Though he was unable to uncover the Zodiac Killer, he was pleased with the progress that he made for the next wave of inspectors that assume his responsibility.

However, he remains optimistic that a crucial piece of evidence, that last piece of the puzzle, will eventually surface and put this case to rest.

“I’m just hoping that one day, somebody finds a diary that was written by our suspect or finds that cowl that he was wearing at Lake Berryessa,” he said.

The Guardsman