Grooming is a part-time activity during a Sprint between the Product Owner and the Development Team. Often the Development Team has the domain knowledge to perform grooming itself.

That line is from the earlier 2011 version of the Scrum Guide.

Product Backlog refinement should involve the Development Team and the Product Owner.

The Product Owner is the grooming decision maker.
Grooming is not a process to break down the items in Sprint Backlog to dailty work.
Grooming refers to a set of three principal activities: adding details, estimating, and ordering.

Does the DT know all the details of each PBI?
Does the DT know which item is most valuable so that the item's priority should be reorder?

Grooming s an ongoing collaborateive effort led by the PO and including the DT, the SM as well as stakeholdes as needed.

PO is the sole responsible for the PB, while the DT is responsible for the estimates.
PO without DT estimates cannot properly order the PB.
It is an accountability issue. PO could delegate part of backlog work but he stills remain accountable.

BTW: DT can spend no more than 10% of its capacity for Backlog Refinement, while the PO can modify the PB any time.

Thank you for clarifying.

Hey, The word Grooming is long back replaced by a word called "refinement".

As Ching-Pei Li summarised it is collection of 3 major activities: Adding details through conversation between DT & PO (+SH); estimates by DT and slicing, as needed; and then finally ordering by PO.

Hi Sowmya, I think we can find the answer in the following questions: Can DT estimate: YES.; Can DT explain : NO. Can DTperform ROI calculations for adding a feature and prioritize - NO. Therefore, DT may have the domain expertize. This may be useful in analysis and coding. But this cannot take away PO's perogatives.