Thailand's prime minister has appeared before the Constitutional Court in Bangkok to defend herself against allegations of abuse of power.
The complaint was filed by senators who said Yingluck Shinawatra's party benefited from improperly transferring her national security chief in 2011.
Ms Yingluck could be removed from office and banned from politics for five years if found guilty.
The decision is expected on Wednesday, the court said after the hearing.
The prime minister's supporters believe the top courts are biased against her and the case is an attempt by the elite to force her from office.
The BBC's Jonathan Head in Bangkok says if the Constitutional Court also bans enough of her cabinet to disable her caretaker administration, her ministers have warned there will be chaos, with large-scale protests by pro-government red-shirts a certainty.
Thailand has seen deadlock since anti-government protests began in 2013. The protesters, who are mainly urban and middle class, want Ms Yingluck's government replaced by an unelected "people's council".
In response, Ms Yingluck called a snap election in February which she was expected to win, but this was disrupted by the protesters and subsequently annulled.
The prime minister is also facing several other legal challenges.
Earlier this year, a different court ruled that she had improperly transferred national security chief Thawil Pliensri in 2011.
He has since been reinstated, although he was originally appointed by the previous administration and has been openly critical of Ms Yingluck's government.
The Constitutional Court will decide whether his transfer violated the constitution.
"I deny the allegation... I didn't violate any laws, I didn't receive any benefit from the appointment," Ms Yingluck told the court on Tuesday.
She added that replacing Mr Thawil was for Thailand's benefit.
Ms Yingluck also faces charges of negligence over a government rice subsidy scheme which critics say was rife with corruption.
Last week, Ms Yingluck's government announced fresh polls on 20 July, but the opposition has rejected the date.
Anti-government protesters allege that Ms Yingluck's brother, ousted leader Thaksin Shinawatra, controls her administration and say Thailand's democracy has been corrupted by money.
Ms Yingluck and her Pheu Thai party remain very popular in rural areas, however, leaving Thailand deeply polarised.