The mother of a vulnerable teenager who suffered a seizure and drowned in a bath at an NHS care unit has called for an overhaul of medical tribunals, saying she felt “retraumatised” after participating in a two-week hearing into her son’s death.

Sara Ryan, whose son Connor Sparrowhawk died in 2013, demanded changes to the “barbaric” treatment of bereaved families at the Medical Practitioners Tribunal Service (MPTS).

“You’re a grieved mother, you’re stripped of any other identity and you’re fair game for any kicking that comes your way and it must happen all the time,” she said. “It’s a terrible treatment of families in this setting. There needs to be change.”

The tribunal in Manchester found that Dr Valerie Murphy, the lead clinician responsible for Connor’s care, failed to carry out any risk assessments on the 18-year-old before he suffered an epileptic fit and drowned while taking an unsupervised bath. Murphy, who now works in Ireland, could face being struck off when the tribunal considers possible sanctions in November.

Connor, who was affectionately nicknamed Laughing Boy, had epilepsy, autism and learning difficulties and was admitted to Slade House, a care unit run by Southern Health NHS foundation trust, on 19 March 2013. He was found unresponsive in the bath less than four months later, on 4 July.

Connor’s death led to the discovery that Southern Health had failed to properly investigate the deaths of more than 1,000 patients with learning disabilities or mental health problems over four years. The trust has accepted responsibility for Connor’s death and will be prosecuted next month by the Health and Safety Executive.

Ryan, an Oxford University academic, said she was left distressed and unwell for days after being questioned by Murphy’s defence barrister, Richard Partridge. She was visibly upset when taking the oath and was reduced to tears under questioning by Partridge, forcing a break in proceedings.

Ryan was repeatedly pressed on what she had told nurses about Connor when he was admitted to Slade House – with the implication, she said, that she should have told nurses her son needed to be supervised in the bath.

Partridge questioned Ryan about her description of Murphy in a witness statement as being “dismissive, arrogant and distant” and asked how she thought that would make his client feel.

He also raised an anonymous blog written by Ryan about Connor and his journey through the care system, which was seen to be critical of some nurses. He asked Ryan whether this blog “might have made people wary of you”.

Ryan said: “I thought it was a barbaric process. It was totally unnecessary. The panel should have stepped in and stopped the questions by the barrister. I thought they were unpleasant, needly, they didn’t contribute towards the allegations, they didn’t shine any light on anything apart from trying to present me as shaky and unreliable.”

Ryan, an academic researcher of autism and learning difficulties, said she felt offended by the tribunal’s finding of fact which said “her memory may have been affected by the major trauma she experienced in the loss of her son”. She said: “I found that so offensive given they sat through me being retraumatised for two hours. They don’t seem to see people as human beings at all.”

Partridge did not respond to a request for comment. A spokeswoman for the MPTS said: “We are sorry to hear how upsetting Dr Ryan found the process of giving evidence to the tribunal. The role of a witness is crucial in giving a tribunal a first-hand account of what has happened in a case, so they can establish whether a doctor is safe to practise. It’s important that account is thoroughly explored and tested.

“However, we do understand that giving evidence can sometimes be distressing which is why we and the GMC offer a support service to all witnesses before they attend a tribunal.”

An inquest jury in 2015 found that a number of serious failings by Southern Health NHS foundation trust contributed to Connor’s death. The tribunal in Manchester heard that a plan had been drawn up that included observations of him to be carried out every 10 minutes because of his epilepsy.

A month before Connor died, a decision was made at a care plan hearing to cut observations to once an hour, even though he had recently bitten his tongue, which could have indicated a seizure.

Ryan said: “It’s almost like if you’re learning disabled the usual rules don’t apply. Richard [Huggins, her husband] and I have always said we’d have been better off taking Connor to the McDonald’s on Green Road roundabout, up the road from us, and leaving him there – he would have been looked after better. It is a terrible indictment of the NHS.”