A teenager accused of bringing the computer systems of a major American port to a halt said the authorities had not carried out a thorough investigation.
Mr Caffrey claims the equipment used by police was inadequate
Aaron Caffrey, 19, of Fairlane, Shaftesbury, in Dorset, claims a virus planted in his computer carried out the attack on the port of Houston in Texas.
On Friday he said there was no way investigators could have checked every file on his computer in their search for the virus.
Mr Caffrey denies one charge of unauthorised modification of computer material.
The scheduling computer system at the port - the eighth largest in the world -
was bombarded with thousands of electronic messages on 20 September, 2001.
The attack left the port's web service inaccessible to groups which rely on its crucial data such as shipping pilots, mooring companies and support firms responsible for helping
ships navigate in and out of the harbour.
Mr Caffrey claims a virus planted on his computer was responsible for the attack on the port and criticised authorities for not finding it during their investigation.
"They were being very suggestive to say they knew what the virus would be," he told the court.
"I put it to them, did they look at every existing file on my computer, and I am quite sure the answer is no.
"Therefore, they did not carry out a thorough investigation," he said.
Mr Caffrey said the anti-viral scanning equipment used on his machine did not have the capacity to detect all the existing viruses.
"It's a race between hackers, crackers and anti-viral agencies, and usually the hackers and crackers will be ahead because that's why the anti-viral agencies exist," he said.
On Thursday he told the court that an unidentified third party had planted the
instructions - known as an attack script - on to his website without him
The case continues.