The prosecution of the parents of a Muslim convert dubbed "Jihadi Jack" has been described as "inhumane to the point of being cruel", a court heard.
John Letts, 58, and Sally Lane, 56, are accused of sending or trying to send their son Jack money after he had joined Islamic State.
Defence counsel Henry Blaxland QC said the parents from Oxford "have for all intents and purposes lost their son".
Mr Letts and Mrs Lane deny three counts of funding terrorism at the Old Bailey.
"This prosecution does absolutely nothing to further the prevention of terrorism," Mr Blaxland told jurors as he summed up.
"In fact it runs the risk of undermining the fight against terrorism because it runs the risk of bringing the law into disrepute.
"This prosecution is completely inhumane to the point of being cruel."
Earlier Mrs Lane's counsel Tim Maloney QC said a note sent between officers in December 2015 gave Jack Letts's parents the right to send their son money.
It said: "John Letts has been informed that they can send Jack funds if there is a genuine belief he needs assistance to leave Syria."
The note added Mr Letts and Mrs Lane needed to "capture all their communication with Jack" and remain open with police.
Mr Maloney said it was "crystal clear to any reasonable person that they had permission to send it if it was to get Jack out".
But he added the pair were given ambiguous advice three days later in a written notice which said: "The police do not endorse or authorise the sending of any monies to Jack Letts."
On Wednesday prosecutor Alison Morgan QC told jurors: "Parents turning a blind eye to the obvious is not a defence."
During the trial the court heard about a Facebook post purportedly posted by Jack where he talked about wanting to decapitate an old school friend.
It also heard how Mrs Lane received messages from her son, who converted to Islam aged 16, saying he wanted to leave Syria and asking for money.
She attempted to transfer £1,000, which she said was to help get him out of danger. Five days later, she was arrested.
The trial continues.