A serving Dyfed-Powys Police officer has admitted a charge of possessing an indecent image of a child.
Mark Bretherick will be sentenced in October
Mark James Bretherick, 33, from Forden, near Welshpool, admitted before Swansea Crown Court downloading the image from the internet.
The police sergeant, who is currently suspended, will be sentenced next month after a probation report is prepared.
Judge Christopher Morton granted bail but warned him that did not mean a prison sentence would not be passed.
His barrister Michael Mather-Lees said Bretherick fully understood the powers of the court.
He was accused of downloading the category three indecent image between 20 October, 2005 and 8 March, 2006.
Bretherick had been due to stand trial on Monday but, following a day of legal wrangling, he admitted one charge of possessing an indecent image of a child on his personal laptop.
The court ordered that 17 other charges of possessing child pornography should remain on file and no further action taken.
The move came after the prosecution acknowledged the impossiblity of proving the images were downloaded after a change in the law.
Until 11 January 2001, the possession of such indecent images of children were only dealt with by magistrates' courts.
After that date, the change meant that they were dealt with only in crown courts.
Bretherick had denied 17 other charges
Jim Davis, prosecuting, told the court that the images in question were found on two laptops in Bretherick's possession.
The offences were alleged to have taken place between February 2001 and March 2006 but a Time laptop seized by the police had 17 images which could have been downloaded before the change in the law.
It had only subsequently been accessed on a few occasions.
Bretherick had always denied the 17 charges.
'Remain on file'
A second Rock laptop bought by Bretherick in October 2005, was found to contain one indecent image of a child in thumbnail form.
It, therefore, must have been downloaded after the change in the law.
It was to this offence that Bretherick pleaded guilty.
Mr Davis said: "The prosecution's view is that in the light of the defendant's plea we will not pursue the remaining counts to trial and they should remain on file."
He said the presence of the illegal thumbnail photo proved that a full-size image "must have been deleted at a previous time."
Sentencing of Bretherick, who is normally based at Newtown Police Station in Powys and was released on conditional bail, is scheduled for 1 October.