Who among the following was not associated with the Kakori case?

The Kakori Conspiracy Case is the specific criminal case that followed the train-robbery action of 9 August 1925 near Kakori, carried out by members of the Hindustan Republican Association (HRA) to raise funds for the armed freedom struggle. Being associated with the Kakori case means being one of the individuals formally named as an accused and tried in that specific 1925 action and its subsequent conspiracy trial.

Applying this to the four names given: Ramprasad Bismil, Ashfaqullah Khan, Rajendra Lahiri, and Roshan Singh were all named accused in the Kakori Conspiracy Case and were sentenced to death (Ashfaqullah Khan in a later supplementary trial after his December 1926 arrest in Delhi). Bhagat Singh was a member of the same revolutionary organisation, the HRA (renamed the Hindustan Socialist Republican Association, HSRA, in 1928), but he was not one of the accused named in the Kakori Conspiracy Case; the criminal cases in which he himself stood trial were the later Lahore Conspiracy Case (the killing of J. P. Saunders, 1928) and the Central Assembly Bombing case (1929).

• Ashfaqullah Khan: an HRA member who evaded arrest until December 1926, and was convicted in a supplementary Kakori trial.

• Ramprasad Bismil: the HRA leader who planned the 9 August 1925 Kakori train action and was convicted in the main Kakori trial.

• Rajendra Lahiri: an HRA member convicted in the Kakori trial for his part in the 9 August 1925 train action, and was the first of the four to be executed, on 17 December 1927.

Because the list of accused in the Kakori Conspiracy Case does not include Bhagat Singh — who stood trial instead in the later Lahore Conspiracy Case and Central Assembly Bombing case — he is the one among the four not associated with the Kakori case.