But an environmental group has labelled this a "desperate attempt" to have evidence excluded and has compared it to "throwing stones in a glass house".
The panel considering the Australian mining company’s fast-track application for its proposed Central Otago mine signalled it would hold expert conferences this month.
These were intended to reach agreement between expert witnesses, narrow points of difference and produce joint statements identifying areas of agreement and disagreement.
Last month, it invited all parties engaging expert witnesses to identify who should participate in these conferences.
But in a memorandum of counsel on behalf of Matakanui Gold Ltd — a wholly-owned subsidiary of Santana — concerns were raised about two witnesses: James Higham and Elizabeth Steven.
Ms Steven had appeared to share — under an account named "Anne Steven" — upcoming public meetings to a community page held by Sustainable Tarras "who have consistently expressed opposition to the project", counsel said.
Prof Higham appeared to make comments encouraging people to sign Sustainable Tarras' petition opposing the project, share anti-mining content and circulate content advocating against the project and supporting opposition to it.
Counsel argued the social media activity aligned both experts "with an advocacy campaign opposing the project".
"We submit this raises concerns as to the impartiality, independence and bias of these experts."
The memo prompted the panel to issue a minute requesting responses from both Sustainable Tarras and the Environmental Defence Society (EDS).
Panel chairman Matthew Muir KC said Ms Steven’s social media activity appeared to be limited to sharing posts on a community Facebook page.
"However, [the panel] notes extensive social media commentary by a ‘James Higham’ which in tone and content would ordinarily call into question whether such person possessed sufficient impartiality and independence to be an appropriate participant in expert conferencing."
Sustainable Tarras chairwoman Suze Keith said the panel would determine the extent of Prof Higham’s involvement.
"It speaks volumes that rather than address many of the substantive issues raised by Prof Higham and numerous other experts, Santana Minerals has spent hours trawling social media to try and get the panel to exclude him."
EDS chief executive Gary Taylor said Ms Steven’s posts neither expressed opinions nor gave rise to any bias.
"Claiming so is a desperate attempt by the applicant to exclude important independent landscape evidence from the process," Mr Taylor said.
"Landscape impacts are serious and should weigh against approval.
"The applicant is throwing stones in a glass house."
Santana Minerals has also requested that two other experts who own land adjacent to the proposed project area do not participate in the conferences.
The panel has requested responses from Sustainable Tarras and EDS by this morning.
