The publication last week of the serious case review into the death of seven-year-old Toni-Ann Byfield meted out a stinging rebuke to the court-appointed guardian for failing in her basic duty of protecting the child's welfare.

It found that the unnamed guardian should have adopted a more "challenging and independent" position, considering the "questionable evidence" she had received (news, page 10, 6 May 2004). The report was prepared by a panel of experts chaired by David Lambert, the independent chair of the Norfolk area child protection committee.

Toni-Ann, who was in the care of Birmingham social services, was shot dead in a London hostel last September along with convicted drug dealer Bertram Byfield - a man who at the time was thought to be her biological father. She had been living under a kinship care arrangement with Byfield's aunt in London since August. Unsupervised contact with him was allowed.

A backlog of cases prevented the Children and Family Court Advisory and Support Service (Cafcass) allocating a guardian at the time of Toni-Ann's first care proceedings hearing in December 2002. Consequently, the guardian was not appointed until after the third court hearing in February 2003 and as a result "never really fully engaged with the case", the report adds.

Cafcass has taken responsibility for the mistakes and revised its child protection policy and procedures and reiterated to guardians what is expected of them. A recruitment drive in the West Midlands has also eradicated delays in appointing guardians to children's cases. In late 2002 there were 67 unallocated cases.

Despite these improvements, some legal experts believe the case highlights fundamental problems with Cafcass.

The service refused to detail the experience Toni-Ann's guardian had, confirming only that she was a qualified social worker who had worked with children and families.

But critics point out that when Cafcass was established in April 2001 the length of child protection experience required to become a guardian was reduced from five years to three.

Liz Goldthorpe, chair of the Association of Lawyers for Children, has been worried about guardians' levels of experience, training and qualifications for some time. She says: "There are some extremely good Cafcass guardians, but if you lower the threshold [for becoming a guardian] you have to compensate by having good quality training."

Alison Paddle, chair of guardians' organisation Nagalro, agrees this has led to the appointment of some guardians with less experience, which has affected their ability to do the job.

She says: "You need to be sure of your ground and know how local authorities work. You also need to have managers who understand these things. For that everyone needs to have the practical experience, knowledge base and confidence to follow that through and justify what you are saying in court is based on evidence."

The well documented contract problems with self-employed guardians, which developed soon after Cafcass's inception, has also resulted in some experienced guardians leaving the service.

Cafcass says Toni-Ann's guardian did not have an excessive caseload and is still working for the organisation. However, when a service is under pressure and failing to cope with demand - as in Birmingham 18 months ago - corners tend to be cut.

With such a large waiting list of cases, guardians were missing the start of care proceedings, "which means you are responding rather than shaping what's happening and always trying to play catch-up", Paddle says. There are still more than 300 cases in England awaiting allocation of a guardian.

When a guardian is appointed midway through a case, a guardian's "instinct" is paramount, says Goldthorpe. "You only really get that through experience."

She says the guardian's role is to ask the "awkward questions no one has thought of or doesn't want to ask" - something the report says Toni-Ann's guardian failed to do.

"She should have been saying 'what's the story here - has anyone checked this man out?' It is like a jigsaw: if you don't know what bits are missing you can't get a complete picture," she adds.

Such failings rarely have the disastrous consequences they did for Toni-Ann, but some fear ill-equipped guardians could be increasing the risk of similar cases arising in the future.