Niemi has held several expert functions in the academic community. She was member of the Scientific Committee of the EU Fundamental Rights Agency (2013-2018) and member of the Finnish Academy Committee on Cultural and Social Sciences (2016-2018). She has evaluated research at the universities of Uppsala and Örebro. She is  consulted as an expert in the Committees of the Parliament and by the Ministries. 

Niemi has been honored as the teacher of the year by students’ organization Pykälä in 2000. She has been the supervisor of 12 doctoral theses. 

Johanna thinks that the most interesting challenge to legal thinking comes from the feminist legal studies that have a close connection to gender studies. She thinks that all lawyers should be familiar with the main ideas about the importance of gender in our thinking and society, including the legal sphere.

Niemi has defended her doctoral thesis in 1995 in personal insolvency law. She is a founding member of the Collaborative Research Network of comparative consumer insolvency law with professors Bill Withford and Iain Ramsay. In 2011-2012 she participated in the World Bank personal insolvency projects. 

Her research interests include criminal procedure, violence against women and human rights. She led several research project analyzing the discourses on gender violence in legal contexts. Her book Criminal Procedure and Violence in Intimate Relationship was published (in Finnish) in 2004. She has analysed the liberal undertone of the Finnish rape law in several articles. She has been co-editor of several books, including Responsible Selves. Women in the Nordic Legal Culture (2001) and International Law and Violence against Women: Europe and the Istanbul Convention (2020). In 2013 she evaluated the Finnish sex purchase ban with LLM Jussi Aaltonen.