It seems the best argument for the suicidal aspect of his death is presented by this report from The Telegraph:Revealed: how Stalin's brutal massacre at Katyn shamed his PoW son into suicide. Some of the same elements are involved such as the electric fence, and the disputes with British officers. But the main gist of this article is the suicide aspect of the 'attempted escape', and its speculation over the cause:
Now it has been disclosed that the Russian artillery lieutenant was so
overcome by shame at the news of his father's massacre of 15,000 Poles
at Katyn in 1940 that he committed suicide by flinging himself on to
the camp's electric fence.
...The disclosure, given credence by Professor John Erickson, the world's
leading authority on the Soviet-German War, has been published in the
latest edition of the Soviet Military Journal.
About the conflict with the British:
A decade ago Professor Erickson and the Russian investigators had
concluded that his death could have been suicide prompted by a violent
confrontation between himself and a group of British prisoners of war.
The new evidence, however, now firmly blames the Katyn massacre.
"This evidence does go some way to exonerating the British officers
whose taunts were believed to have pushed Yakov to breaking point,"
Erickson says, "but it also highlights the devastating effect the
Katyn massacre had on Yakov. He could not live, I believe, with the
accounts he was given of the massacre ordered by his father.
Concerning the shooting:
Though the official SS report at the time indicated that Dzhugashvili
died after he was shot by a guard as he ran towards the wire, it is
now known this was a fictional account compiled to impress Heinrich
Himmler. "The guard certainly shot Yakov four times," Professor
Erickson, who has viewed the evidence, confirms, "but it is now known
that he fired the bullets into Yakov's already dead body."
So this historian believes the shame over the revelation of the massacre at Katyn, as well as conditions in the camp, finally accumulated to the point where Yakov couldn't take it any more.
"It is clear that Yakov, who had become close friends with the Poles
and had made two abortive escape attempts with them, was so distraught
when goaded with the news of his father's massacre of the Polish
officers, which was revealed in German newspapers in 1943, that he
took his life. Driven to despair by the horrific conditions in the
camp - he was emaciated and on the point of starvation - and the
strain of the propaganda campaign the Germans had involved him in, the
news that his father had sanctioned the Poles' murder was the final
"Though the Poles were killed at Katyn in 1940, their bodies were not
discovered by the Germans until March 1943. When a camp guard showed
Yakov the newspaper reports of the discovery, taunting him with the
words, 'Look what you bastards did to these men. What kind of people
are you?' Yakov was devastated. He was at the end of his tether. A
month later, on April 15 1943, unable to live with the shame, he took