(Adds comment from Palantir, paragraphs 5 and 10)
WILMINGTON, Del., Feb 22 (Reuters) - Data analytics and security company Palantir Technologies Inc must open its books to early investor Marc Abramowitz, who wants to investigate possible fraud and mismanagement at the highly valued private U.S. company, a judge ruled on Thursday.
Abramowitz sued the secretive firm, known for helping the U.S. government track down al Qaeda leader Osama bin Laden, after a 2015 falling out with Alexander Karp, the company's chief executive officer.
The lawsuit alleged that Palantir wrongly barred Abramowitz and others from selling stock in the privately owned company, while permitting sales by Karp and Chairman Peter Thiel.
Judge Joseph Slights of the Delaware Court of Chancery ruled that Abramowitz demonstrated "a proper purpose of investigating potential wrongdoing and a credible basis to justify further investigation."
Palantir said in a statement it was pleased by the outcome, saying it denied Abramowitz's requests "beyond limited company disclosures."
Palantir does highly confidential work for U.S. defense and intelligence agencies, helping them track down terrorists and uncover financial fraud.
The company raised $880 million in funding in 2015 and was estimated to have a valuation of about $20 billion at that time.
Abramowitz, through the KT4 Partners LLC fund he manages, invested an initial $100,000 in Palantir in 2003, which, after subsequent investments, is estimated to be worth $60 million, according to Slights' 50-page opinion.
Abramowitz enjoyed a close relationship with Karp until 2015, when Karp "verbally abused" Abramowitz and accused the investor of stealing Palantir intellectual property, according to the opinion.
Soon after, Abramowitz tried to sell his Palantir stock, but he alleged that the company blocked the deal by offering the potential buyer newly issued stock instead, the ruling said.
Abramowitz began demanding information from Palantir as he considered suing the company for blocking the sale of his stock. In response, Palantir sued Abramowitz in September 2016 for allegedly stealing trade secrets, according to Slights.
Palantir said on Thursday it would continue to pursue the theft case against Abramowitz.
In March, Abramowitz brought his Delaware case.
Palantir had argued that Abramowitz should be denied information because he was likely to use it to build his lawsuit over the blocked sale.
Slights ruled that Abramowitz could investigate Palantir's lack of annual meetings, corporate amendments that limited KT4's rights and the company's sales of stock. But the judge would not allow Abramowitz to probe Palantir's valuation or Karp's compensation. (Reporting by Tom Hals in Wilmington, Delaware; Editing by Lisa Shumaker and Tom Brown)