[...] Could the supine be used without "har/hade"? [...]
It certainly could, but in subordinate clauses only. This is very common in Swedish, absolutely correct, absolutely idiomatic. Even
Wikipedia has a good explanation.
However, for the sentence quoted I agree with
MattiasNYC that "att det ledde" would read better. No, come to think of it, and having googled, the usage of
lett here is completely incorrect, for it messes up the tenses.
[...] där Thomas Larkin tacklade Daniel Paille så svårt att det lett till åtal och rättegång.
The tackle led to prosecution and trial later. Larkin was
recently acquitted by Gävle tingsrätt, four years later. The sentence insinuates that the 2017 tackle had led to prosecution and trial when it happened. This is sheer nonsense, the journalist introducing the fact that prosecution and trial had taken place when the sentence was formulated. A simple
nu would save the sentence:
[...] där Thomas Larkin tacklade Daniel Paille så svårt att det nu [har] lett till åtal och rättegång. The problem with the sentence is that the use of
tacklade (in preterite) makes one expect that
lett should be understood as
hade lett (in 2017). But the journalist wants to say that the tackle
has led to prosecution and trial (now, in 2021).
As for the perfect/pluperfect without
har/hade in subordinate clauses, let me adduce two examples I just made up:
Jag vet att hon kommit. = Jag vet att hon har kommit.
Jag visste att hon kommit. = Jag visste att hon hade kommit
