Bradley Manning's maximum possible sentence for leaking state secrets to WikiLeaks was cut from 136 years to a possible 90 years on Tuesday, marking a rare victory for the defence in a trial that has so far swung almost exclusively in the US government's direction.

The judge presiding over the court martial, Colonel Denise Lind, granted the most elements of a defence motion calling for some of the 20 counts for which Manning has been found guilty to be merged on grounds that they repeat each other. In the motion, defence lawyers argued that the government had taken single acts of criminality and split them into several separate violations – thus multiplying the possible sentence.

"By dividing this ongoing act into two separate specifications," the motion says, referring to the soldier's transmission of the US embassy cables to WikiLeaks, "the government takes what should be a 10-year offence and makes it a 20-year offence and unfairly increases Pfc Manning's punitive exposure".

Lind granted all defence requests to merge counts, except specifications four and six of charge II that relate to stealing and purloining of the Iraq and Afghan warlogs. Reporters present in the court said they were unable to record details of the judge's ruling because she read her judgment so fast.

In previous hearings, the Guardian has counted that she reads at a rate of 180 words per minute. In one session, even the stenographers employed by the Freedom of the Press Foundation as a way of injecting public accountability in the trial process struggled to keep up with Lind as she read.

"Judge Lind recitation of her ruling on merging of sentencing charges was ridiculously fast. NO respect for the public and press," tweeted the independent journalist Alexa O'Brien. Nathan Fuller of the Bradley Manning Support Network concurred: "Judge read merger ruling too fast to transcribe."

The merging of offences is the first glimmer of hope for the army private since he was found guilty of 20 of the 22 counts that he faced as a result of leaking more than 700,000 documents to the anti-secrecy website. He was found not guilty on the most serious charge, "aiding the enemy", and of another count relating to the transmission of an encrypted video of a US air strike in Garani, Afghanistan.

Lind is presiding over the case alone, in the absence of a jury, at the request of Manning. The sentencing phase, a form of mini-trial, is expected to last at least two more weeks, with the defence planning to call more than 20 witnesses once the prosecution has completed its sentencing testimony.