Wanjiru’s niece, Esther Njoki, told the BBC that the family had learnt of the postponement through the UK embassy and had received no official explanation.
“We have exercised patience and endured uncertainty for years, but our patience is now being taken advantage of,” she said in a statement.
“Agnes deserves justice. Her daughter Stacy deserves answers about what happened. And as a family, we deserve to be treated with dignity and kept informed about proceedings that profoundly affect our lives.”
The family said it had already raised money and made arrangements to travel to the UK for the hearing, which was due to take place in three weeks.
It is now calling on the authorities to expedite the proceedings, warning that the latest postponement means the case will enter its 15th year without a trial.
The family said a UK court was expected next week to give the reasons for the hearing delay.
Wanjiru disappeared in March 2012 after spending an evening at a hotel in Nanyuki, about 200km (124 miles) north of the capital, Nairobi, where British soldiers were stationed for training.
Her body was found nearly three months later in a septic tank at the hotel. She had suffered stab wounds to her chest and abdomen and left behind a five-month-old daughter.
A Kenyan inquest concluded in 2019 that she had been unlawfully killed by one or two British soldiers.
In September 2025, a Kenyan High Court issued an arrest warrant for a British national after prosecutors presented evidence they said justified bringing murder charges.
Purkiss’ lawyers said he intended to contest his extradition to Kenya.
He appeared at Westminster Magistrates’ Court in February via video link, where he was further remanded in custody.
Last year, the then British Defence Secretary John Healey met Wanjiru’s family during a visit to Kenya and pledged his government’s support for efforts to secure justice.
The UK government has previously said it remains committed to helping the family, but would not comment on ongoing legal proceedings.
