Police officers who restrained and pepper-sprayed Edir da Costa on the night he was fatally injured used unusual force for a stop and search and failed to give him first aid quickly enough, an expert witness at the inquest into his death has said.

Joanne Caffrey, a specialist in restraint who was a police officer for 23 years, said it was not necessary for officers to have struck the 25-year-old father of one or jabbed a pressure point in his neck while attempting to restrain him in Beckton, east London, for a stop and search under section 1 of the Police and Criminal Evidence Act.

She also said that police involved in the restraint failed to establish a “safety officer” to take charge of the situation, in order to ensure that best practices and safety procedures were being followed.

There is disagreement over when officers became aware that Da Costa was concealing drugs in his mouth, but Caffrey said they should not have discharged CS spray in his face that if they had been aware of it.

Medics who tried to save Da Costa’s life on the night of 15 June 2017 found a plastic bag containing dozens of wraps of heroin and crack cocaine blocking his airway. Da Costa, who was also known as Edson, was taken to hospital, where he was placed in intensive care, but he died six days later.

On Tuesday, Caffrey told Walthamstow coroner’s court that it appeared from the evidence she had seen that the five plainclothes officers who stopped Da Costa used force beyond that suggested in guidance for a section 1 stop and search.

“The general core principle is that police officers should aim for the cooperation of the person,” she said. Caffrey said “I would have been having concerns … thinking this is a stop [and] search and it’s suddenly going out of control” if she had been the sergeant in charge of the unit carrying out the search.

“I would be wanting to get involved to try to calm things down … Even if the person initially resists, the officers should be trying to get the person’s cooperation,” she said.

Instead, according to the evidence heard so far, officers struck Da Costa several times and attempted to manipulate a pressure point in his neck to force him to comply with attempts to handcuff him.

Strikes of the kind used by officers were acceptable if used in self-defence, Caffrey told the court. Officers had said that intelligence of the crime situation in the area that night had led them to believe that suspects may have been carrying weapons.

But Caffrey said: “There’s always the fear that a person has a weapon. However, [the law] is very clear that any use of force has got to be based on objective grounds [such as the suspect apparently reaching for a weapon]. What officers should not be doing is just assuming that everybody has a weapon and therefore that gives them the right to use force.”

Caffrey said that when Da Costa spat drugs out of his mouth, after being tackled to the floor and wrestled by four officers, the focus of the police involved should have immediately turned towards a medical emergency.

Instead, the inquest has heard, officers continued to restrain Da Costa, ordering him to “spit it out” and again using a pressure point in his neck in an attempt to force him to open his mouth.

Even after Da Costa became unresponsive, it was only after armed officers arrived on the scene and took over care for his welfare that it was established that he had stopped breathing and attempts to resuscitate him began.

The inquest continues.