Ismail Abedi, 28, whose whereabouts are currently unknown, had refused to co-operate with the probe into the attack on the Ariana Grande concert in 2017.
South Shields couple Chloe Rutherford, 17, and boyfriend Liam Curry, 19, were among five people from the North East who died as a result of the blast, which also included Hartlepool mum Jane Tweddle and Philip Tron, 32, and his partner’s daughter Courtney Boyle, 19, both from Gateshead.
Abedi was listed for trial at Manchester Magistrates’ Court on Thursday under the name Ishmale Ben Romdhan, but did not attend and was found guilty by District Judge Jack McGarva of failing without reasonable excuse to do something required by a Section 21 notice.
The judge adjourned the case to August 2 and said if Abedi does not attend that hearing a warrant will be issued for his arrest.
He said: “The court is bound to consider passing a custodial sentence.
“There is a very high level of public interest in ensuring people co-operate with public inquiries.”
He added Abedi could have given evidence on “some really key points that the families of the deceased would have really appreciated having answers to”.
The court heard that Abedi had previously said he did not want to answer the inquiry’s questions because he was concerned about risk of self-incrimination, had already been questioned by police, and was concerned for the safety of himself and his family.
The IT worker was described as a key witness for the inquiry, able to answer questions about the radicalisation of his younger brothers, Salman, who carried out the suicide attack which killed 22, and Hashem, who has been jailed for life for his part in the bomb plot.
Bereaved families labelled Ismail Abedi a “coward” for refusing to answer questions.
Nicholas de la Poer QC, prosecuting, said: “The prosecution submits that you can be sure from the chronology that the defendant from the first was determined not to co-operate with the inquiry.
“He has prevaricated, he has obfuscated, he has thrown up every obstacle he could think of.
“When those failed, he fled the jurisdiction."