Mr Ditchfield, who argues cannabis should be legalised, owns the website northwalespolice.com.
He bought the internet domain name two years ago, after spotting it was for sale at an auction. He paid £12.50 for the title.
A police spokesman said at the time there was an infinite number of domains and it would have cost the public hundreds of thousands of pounds for the force to buy them all.
Last year Mr Ditchfield, however, also snapped up northwalespolice.co.uk.
The force's official website is north-wales.police.uk.
Earlier this week, to his amazement, Mr Ditchfield received an email with an internal application form for a post as observer with NWP's helicopter.
As evidence of her power of observation, the policewoman pointed to the fact she spotted Khan's bloodstained knife while out jogging near Ruthin, a few hours after Mr Dodd was killed at Ffrith Beach in March, 2003.
She wrote: "I made the decision to return to the location and seize the knife in the appropriate manner.
"Following forensic examination, two DNA profiles were obtained, the deceased's and the defendant Paul Michael Khan."
Khan, who was on release from a secure unit, was subsequently convicted of Mr Dodd's murder.
Mr Ditchfield told the Daily Post he could hardly believe his eyes when he read the email.
"It makes one wonder about the officer's powers of observation if she can't even identify her own force's address," he said.
He said he had not yet decided what to do with the document.
The police officer, who is not being named, has declined to comment.
A North Wales Police spokeswoman said: "This was an unfortunate mistake waiting to happen.
"Mr Ditchfield knew exactly what he was doing when he bought the site. This is an irresponsible use of the internet."
Mr Ditchfield also revealed last year he received a report from another police officer about a fire in Wrexham.
