Here are 10 facts in this story:
The former cop has sued Narendra Modi, BJP chief Rajnath Singh, party spokesperson Meenakshi Lekhi, and eminent scientist Dr S Nambi Narayanan.
Mr Sreekumar retired as the top cop in Gujarat in 2007.
He was a senior officer in the Intelligence Bureau in Kerala in 1994 when Dr S Nambi Narayanan and another scientist with the Indian Space and Research Organisation (ISRO) were arrested on espionage charges.
In 1996, the CBI said they were innocent.
The CBI then recommended action against some of the officers who had investigated the case.
At a press conference last week, BJP spokesperson Meenakshi Lekhi alleged that Mr Kumar was exonerated because he fabricated evidence to implicate Mr Modi in the communal riots of Gujarat in 2002.
At the time, Mr Kumar was the head of the Gujarat police's intelligence wing.
In September, Narendra Modi met Dr Nambi Narayanan in Thiruvananthapuram. The scientist has been campaigning for compensation for the nearly two months that he spent in jail, where he says he was allegedly tortured.
In his lawsuit, Mr Kumar says the scientist referred to him recently as a CIA agent.
Mr Kumar says that the BJP has damaged his reputation "by digging out an old closed case of 1994 related to espionage affecting the national interests of country".
Pics: PM Modi's "Special" Raksha Bandhan Celebration With His "Young Friends" After Rahul Gandhi's Attack On Lateral Entry, BJP's "UPA's Time" Reminder Let's Work Unitedly To Confront Pressing Challenges: PM Modi To Global South Indian Airports, Borders On Alert As Global Mpox Cases Rise: 10 Points The Questions CBI Asked Kolkata Hospital Ex-Head About Doctor's Rape-Murder "My Intention Was To...": Sudha Murty Clarifies Raksha Bandhan Post West Bengal Governor Arrives In Delhi, Likely To Meet President Murmu Study Abroad: Top 10 Universities In Japan Based On Latest Ranking Finances Of Kolkata Hospital During Ex-Principal's Tenure Under Scanner Track Latest News Live on NDTV.com and get news updates from India and around the world.