[3] On 17 May 2016, the Times of India published an article reporting that a litigant had written to the Chief Justice of India and other judges of the Supreme Court, complaining that Justice Mittal's disposal of cases was slow and constrained by her involvement in administrative work, as a result of which she allegedly did not sit in court for a sufficient period of time to hear matters, and that this had personally affected the litigant.
[10] Mittal wrote a number of significant judgments as a judge at the Delhi High Court, many of which concern the conditions of service and recruitment in military and para-military forces in India.
In 2011, along with Justice R. Midha she passed a significant ruling concerning the rights of transgender individuals, holding that a woman with a congenital hormonal anomaly had been unfairly discriminated against when she was prohibited from joining the Sashastra Seema Bal (a border patrol organisation) as a female constable.
[11] In 2013, along with Justice Deepa Sharma, she held that colour-blindness could not be grounds for discrimination in the context of promotion in the Central Reserve Police Force.
[16] However, in 2016, along with Justice IS Mehta, she laid down principles that courts should follow in hearing cases concerning pleas for court-ordered paternity tests.
[17] In 2014, along with Justice J.R. Midha, she dismissed an appeal filed in the Nitish Katara murder case, upholding the trial court's conviction of Vikas Yadav, the son of Uttar Pradesh politician D.P.
[20] In August 2018, she and Justice C. Hari Shankar found that the provisions of the Bombay Prevention of Begging Act, 1959 were largely unconstitutional, and struck it down.
[26][27] In her letter she noted that the passing of the Jammu and Kashmir Reorganisation Act 2019 had resulted in the need to transfer a number of pending service matters from the High Court to such tribunals.
[26] The publication of her letter met with opposition from the Chairman of the Central Administrative Tribunal, Justice L. Narasimha Reddy, who disputed the need for a separate bench in Jammu and Kashmir at that time.
[31] Mittal has served as a member of the Advisory Board constituted under the Conservation of Foreign Exchange & Prevention of Smuggling Act, 1974 (COFEPOSA).
[3] Justice Mittal also serves on the editorial advisory board of the National Law University Delhi's Journal of Legal Studies.
[38] In 2017, Mittal was one of the recipients of the Nari Shakti Puraskar, a civilian honour presented by the Ministry of Women and Child Development of the Government of India to individuals and organisations contributing to female empowerment.