Evelyn E. Burwell's family was surprised to learn she voted in the 2012 general and primary elections. They knew she was an avid voter, but she's been dead since 1997.

Burwell is one of about 6,100 deceased people still registered to vote in Nassau County, a Newsday computer analysis shows. The former Wantagh resident, who died at age 74, is also among roughly 270 people that records show voted in Nassau County after dying, a group that includes a man who voted 14 times since his death.

Newsday's analysis of voter registration and U.S. Social Security Administration death records found more deceased registered voters in Nassau County than any other New York county, accounting for nearly a quarter of the 26,500 on the rolls statewide. Suffolk County has about 2,490 deceased people registered to vote, with roughly 50 listed as voting after their death.

The votes attributed to the dead are too few, and spread over 20 elections since 2000, to consider them a coordinated fraud attempt. More likely is what investigators in other states have found when examining dead voter records: Clerical errors are to blame, such as a person's vote being assigned to a dead person with a similar name.

But the sloppy condition of the local voter rolls does suggest that election officials are not utilizing all available methods to maintain a clean list. Besides the dead voters, Newsday's analysis also found more than 842,000 registered New York voters who records show haven't cast a ballot in 10 years. Harvard University professor of government Stephen Ansolabehere, an expert on voter list issues, said those registrations are likely not current.

Ansolabehere said bloated voter lists can cause problems other than fraud, as they are used to establish precinct boundaries, communicate with voters, validate voters at the polls and audit election results.

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The voter roll "interacts with all aspects of the election system," Ansolabehere said. "That's why it's important to keep lists as good and as current as possible."

John E. Ryan, counsel to Nassau County Republican elections Commissioner Louis Savinetti, said he could not say why so many dead voters remain on Nassau's rolls.

"I can't tell you why those numbers are as you found," Ryan said. "I can tell you it's not purposeful on any part."

Nassau Democratic elections Commissioner William Biamonte also had no explanation for the dead voters. Both he and Ryan said Nassau always looks to improve its voter list. "Anything we can do to improve the voter rolls we would participate in," Biamonte said.

Following the 2000 presidential election and its disputed recount, state and federal legislation sought to improve voter list accuracy. That included having state officials coordinate voter list maintenance.

But Newsday's analysis found about 5,820 voters still on New York's rolls who died before the 2000 election.

Both Nassau and Suffolk follow similar procedures in determining whom to purge from their voter lists. State Board of Elections officials send the counties lists of potentially invalid registrations, including those of felons, people who died in New York and people who moved within the state.

"Once the state notifies us, we just delete the person if they are deceased or in jail or out of the county," said Rose Ann Weis, who works with the Suffolk County Republican elections commissioner.

Each county also sends mail annually to all voters and puts them on an inactive list if it's returned undelivered. Voters are on the inactive list for two federal general elections before their registrations are revoked, unless they show up to vote or otherwise contact the county board. Election officials may also purge voters when they register in other states and supply an old Long Island address.

New York is not participating in two programs used by other states to improve the accuracy of their voter rolls.

Seven states recently formed the Electronic Registration Information Center (ERIC), which uses Social Security, vehicle registration, change-of-address and voter-list data to identify ineligible voters. The program, which costs states about $50,000 per year, found 900,000 potentially ineligible voters among its states in its first year, according to the Pew Charitable Trusts, which helped start ERIC.

Another group of 27 states take part in a program known as Crosscheck, which uses registration data to identify voters who have moved across state lines. The free program found 5 million potentially invalid registrations this year, according to its most recent report.

State Board of Elections spokesman Thomas Connolly said he was not aware of whether New York officials have considered joining either program.

Elections officials also learn of invalid registrations when voters notify them.

John Burwell, Evelyn Burwell's son, said he will ensure his mother is removed from the rolls. Burwell, 66, of Levittown, said someone should be held accountable for the condition of the voter rolls.

"If they've been in their job for a long time, and they are not following through, they should not have that job," Burwell said.