Baxter, a dog from Fairfax, is at the center of a trial. A dog walker will face a jury trial in Fairfax County Tuesday for a charge of failing to clean up after the dog. He is held by his owner. (Sarah L. Voisin/THE WASHINGTON POST)

Did Baxter leave his business on Greenwood Court?

A dispute between neighbors in Fairfax County over that perennial suburban pet peeve — unscooped dog poop — has grown so big that the case is set to go to a jury Tuesday.

A dog walker invested $1,200 in her defense, and a supposed eyewitness will testify. A photo of the offending pile will be admitted as evidence.

The fluffy 19-pound Westie-bichon frise mix will stay home.

The case is just one flash point in an increasingly sophisticated, expensive and acrimonious battle over dog waste in the Washington suburbs and beyond. Two Northern Virginia apartment complexes have signed on for PooPrints, a service that collects DNA samples from pooches, taking a “CSI”-style approach to find the culprits of unclaimed messes.

The Fairfax story began on a cold, dark morning in April. Kimberly Zakrzewski, 46, was out walking Baxter, a friend’s dog she often cares for.

Virginia Cornell, a neighbor, said she saw Zakrzewski walk away after Baxter made a mess on the grounds of the Penderbrook complex near Route 50. She called police and filed a complaint under Fairfax’s “pooper scooper” law.

Cornell, who works in the legal profession, said she took a photo of the waste that she plans to submit as evidence at trial, along with testimony from the police officer who took the complaint.

“She was letting the dog poop on purpose because she knew it annoyed us,” Cornell said, referring to herself and a sister who lives with her. “This individual has no respect or regard for anyone else and views herself as above the law.”

Zakrzewski, a stay-at-home mom who often cares for Baxter, said no such incident occurred. She said she carries plastic bags on each walk and never leaves any poop behind.

The dog walker said her attorney will call Baxter’s owner to testify that the dog pile in the photo could not have been Baxter’s — it was the wrong size and consistency. That testimony, she said, will be buttressed by that of another dog walker and Zakrzewski’s husband, Michael, who was with her on the morning in question.

Zakrzewski and Cornell have long had a tense relationship. Records show that Virginia Cornell’s sister, Christine Cornell, filed a criminal complaint accusing Zakrzewski of driving recklessly on the grounds of their complex in 2008. A jury found Zakrzewski not guilty.

“It’s somebody filing nuisance charges to upset and to hurt me,” Zakrzewski said. “That’s how these people spend their life.”

Although the battle between Zakrzewski and Cornell could turn into a battle of witnesses, some apartment buildings and homeowner associations are turning to hard science to prove who isn’t cleaning up after their dogs.

PooPrints works like this: All the dogs in a complex or neighborhood are given a cheek swab to gather their DNA. When a mess is not cleaned up, the property manager sends a sample of the offending poop to PooPrints to match its DNA against the swab database.

The service costs about $30 to register each dog and $60 in addition to test each sample. The property owners typically transfer the cost of the DNA test to the owner of the offending pooch.

Jim Simpson, president of BioPet Vet Lab, which offers PooPrints, said that the Washington area property owners who use the service did not want to be identified but that the buildings are in Falls Church and Ashburn. He said that business is brisk for the Tennessee-based company and that he hopes to expand to the West Coast and Midwest soon.

“Once the program is in place, the reality is few samples are ever tested. It’s a great deterrent,” Simpson said.

But one not without controversy. The board of Scarlett Place, a luxury waterfront condominium in Baltimore, abandoned the idea of using PooPrints last year after residents rebelled. One told the Baltimore Sun that the plan was ridiculous and that he felt as if he were “living in a ‘Seinfeld’ episode.”

Zakrzewski’s misdemeanor case was first heard in Fairfax County District Court. She said she missed the June court date, was found guilty and fined $250. Zakrzewski had the right to appeal her case to Circuit Court, which is where Tuesday’s trial will occur.

She said that she understood the case must appear “absolutely absurd” to outsiders but that she had no choice other than to defend herself against the charges.

Staff writer Tom Jackman contributed to this report.