I find Sugden's approach to this issue rather odd.
In the introduction to the 2nd edition of his Complete History, he refers to an attempt to locate the inquest records for the murder of Emma Elizabeth Smith. Having discovered that no coroner's papers for the old Eastern District of Middlesex have survived he says:
"A ray of hope invigorated my efforts when I discovered that Coroner Wynne Baxter had sent a copy of his inquest papers to the Public Prosecutor, but it was soon extinguished. All that remains today in the records of the Director of Public Prosecutions is a single line entry in a register of cases. In the comments column is the cryptic remark; 'no-one in custody'." Here he gives a reference to DPP 3/7.
Leaving aside the fact that there is nothing cryptic about the comment 'no-one in custody', what is so strange is that Sugden leaves it there, with the inquest papers of Emma Elizabeth Smith. DPP 3/7 is a register of applications to the DPP from 3 October 1887 to 25 May 1888 and thus outside the date range of the C5 ripper murders.
I can't believe that Sugden would not have moved on to DPP 3/8, the register which covers the period 25 May 1888 to 12 February 1889. Had he done so, he would have found reference to Baxter providing papers to the DPP of three C5 Ripper murders plus Tabram. Yet Sugden does not even mention this crucial register!
For the record, DPP 3/8 shows that Baxter forwarded a copy of Tabram's deposition to the DPP on 31 August 1888 (ironically the same day as Nichols's murder). The comment here is "No arrest made" rather than "no-one in custory". Two copies of the depositions from the Nichols inquest were forwarded by Baxter to the DPP on 27 September 1888 at a cost of £3.3.0. Comment also "No arrest made". On 3 October 1888 two copies of the Chapman depositions were forwarded to the DPP. No comment other than that the cost of £4.4.0 had been met. And then on 2 November 1888, at a cost of £5.5.0, copies of depositions from the Stride inquest were sent by Baxter to the DPP, with the register containing the comment "No arrest made".
Presumably the copies of these depositions were all destroyed in due course at the DPP's office but Sugden's approach does make me wonder what efforts he made to track these down bearing in mind that he does not actually even mention them!