Shkreli also told Retrophin investors he planned to produce a generic drug equivalent for one of Retrophin's products, which could harm company revenue, Aselage said.
"The defendant and three of his friends broke into the offices," Aselage said, and then downloaded files from Retrophin's computer servers.
Before being ousted, Aselage said, Shkreli had told Retrophin's board that he wanted a unit within the company to be allowed to operate effectively as a hedge fund trading biopharmaceutical stocks — despite concerns of the board.
"The analogy he gave us was he was a mother lion and he was training his cubs to kill," Aselage said.
Shkreli, 34, is accused of looting Retrophin of tens of thousands of shares of stock as well as cash to give to investors in two hedge funds he previously ran. Prosecutors charge that he defrauded those investors at the funds, whose financial performance was poor at the time he was issuing glowing financial statements.
Under cross examination, Aselage said of Shkreli, "Intellectually he may have the brightest intellect of anyone I've ever run into."
But Aselage went on to say, "There's also a lot of self-aggrandizing ... a lot of ego that comes out of Mr. Shkreli and some insensitivity with how he deals with other people."
"If he likes somebody, he has great people skills, or if he wants to use somebody," Aselage said.
"In day-to-day interactions with other people, he doesn't seem to see other people as important if they don't fit into the scheme of what he wants to do."
Shkreli's lawyer, Benjamin Brafman, asked Aselage why he made positive comments about Shkreli in a Retrophin press release at the same time he supposedly believed Shkreli was acting inappropriately at the company.
Aselage said, "Mr. Shkreli was doing a lot of good things."
"While he was doing some very good things, he was doing some very bad things, that were the tip of the iceberg of what we knew," Aselage said. "What he did well doesn't make him less accountable for what he didn't do well."
In his testimony, Aselage detailed a series of events that led Retrophin members to consider having Shkreli step down as CEO in 2014, and move into another role at the company that would better suit his talents.
'"The ongoing assessment was that while Martin brought a lot of good ideas to the company, he wasn't actually managing the company, and management needed to be brought to the company for it to survive," Aselage said.
"We wanted to put him in business strategy or business development, something where he could still use his interest and his intellect, but not be responsible for running the company," Aselage said.
He said Retrophin's board had learned that Shkreli had used company funds to hire private investigators to dig up information on individuals, and some board members had "significant concerns about this ongoing use of Twitter" to talk about Retrophin.
Shkreli's tweets "tended to be immature and not particularly relevant and not particularly appropriate for the CEO of a publicly traded company," Aselage said.
In one case, he said, Shkreli tweeted while the stock market was open that he was having "the best day of his life," which worried Aselage and other directors that Shkreli's followers would believe he was telegraphing nonpublic information about Retrophin stock.