DENVER (CBS4) – A CBS4 investigation has found multiple cases of dead men and women voting in Colorado months and in some cases years after their deaths, a revelation that calls into question safeguards designed to prevent such occurrences.

“We do believe there were several instances of potential vote fraud that occurred,” said Colorado Secretary of State Wayne Williams after reviewing the CBS4 findings. “It shows there is the potential for fraud.”

The cases of dead men and women casting ballots ranged from El Paso County in southern Colorado to Denver and Jefferson County. CBS4 discovered the fraudulent voting by comparing databases of voting histories in Colorado against a federal death database.

The CBS4 investigation has triggered criminal investigations in El Paso and Jefferson counties along with a broad investigation by the Colorado Secretary of State’s office.

“It’s not a perfect system. There are some gaps,” acknowledged Williams.

One of the most glaring cases was that of Sara Sosa in Colorado Springs. She died on Oct. 14, 2009. However, CBS4 uncovered voting records that showed ballots cast for Sosa in 2010, 2011, 2012 and 2013. Her husband, Miguel, died on Sept. 26, 2008. But CBS4 unearthed records showing that a vote was cast in his name the next year, 2009.

“That’s illegal,” said El Paso County Clerk and Recorder Chuck Broerman, who called the CBS4 findings “very serious.”

“I was shocked and surprised at this,” said Broerman. “This cannot happen. We cannot have this here or anyplace in our country. Our democracy depends on it. People have spilled their blood for the values and underpinnings and beliefs of this country.”

Broerman said after their deaths, the Sosas remained on active voter rolls and mail ballots were still sent to their home because they did not meet the criteria to have their names deleted from eligible voter rolls.

“Somebody was able to cast a vote that was not theirs to cast,” concluded Broerman.

CBS4 visited the Sosa’s Colorado Springs home and contacted their daughter, Sarilu Sosa-Sanchez, who refused to discuss the fraudulent ballots.

“Go talk to someone else,” said Sosa-Sanchez.

When told CBS4 was investigating voter fraud, the woman said “I don’t know what that has to do with me.”

Voting officials have now asked the Jefferson County District Attorney to look into another dead voting case discovered by CBS4, that of Nell Cluck.

“Ma” Cluck, as she was known, died Feb. 1, 2009. However, nine months later Cluck managed to vote in an election.

“I think mom would be really unhappy about it,” said her son, Jim Cluck. “I think mom would be really disheartened to know somebody used her name to do something that she didn’t have any input into. If mom passes away and nine months later someone votes for her, that’s not right.”

A spokesperson for the Jefferson County District Attorney’s office confirmed the Secretary of State had recently requested a probe of the Cluck case.

Then there’s John Grosso of Denver, a father, grandfather and World War II veteran who died Dec. 13, 2004. Records show though that Grosso then voted at a polling place two years later, in a 2006 primary election.

“I think that’s a disgrace,” said his son, John.

“The man is dead. He can’t vote. Somebody is cheating.”

Administrators with the Secretary of State’s Office believe Grosso’s vote may have been an error by an election judge.

But the broader question is why Grosso — and dozens of others — were still listed as active voters months and sometimes years after their deaths. State voting officials say they can only delete names from voting rolls if a number of precise criteria from death databases are met: names must be spelled precisely right, dates of birth must be correct and addresses must match. They say in many cases minor errors on the voter rolls or death databases leave election officials no choice but to leave dead people registered, leading to potential fraud and mistaken votes.

Out of approximately 2 million votes cast in Colorado’s last election cycle, 8,000 ballots were not counted when signatures did not match. The importance of finding and weeding out fraudulent votes is underlined by the 2002 election in Colorado’s 7th Congressional district. That race was decided by 121 votes out of more than 175,000 that were cast. In Ohio in 2010, a tax measure passed by just two votes.

Following the CBS4 investigation, the Colorado Secretary of State’s office reviewed the CBS4 findings and confirmed at least 78 dead voters remained eligible to vote. Lynn Bartels, a spokesperson for the Secretary of State’s office, said county clerks were notified and told to immediately remove those 78 names from voter rolls. Bartels said “It’s not clear why” those dead citizens were still being listed as eligible voters.

Chuck Broerman said what CBS4 found “undermines our system. It does dilute your vote in a small way.”

Williams said measures implemented in 2015 should reduce the number of dead voters casting ballots in Colorado, but he noted that the CBS4 investigation indicates further measures might be necessary.

“It’s not a perfect system,” said Williams, “It is impossible to vote from the grave legally.”