SAN FRANCISCO (CBS SF) — A senior PG&E engineer testified at the utility’s criminal trial in federal court in San Francisco Thursday that he always used his “best judgment” in supervising pipeline tests and never knowingly violated regulations.

Natural gas supervising engineer Todd Arnett, a 25-year employee of the company, was asked by PG&E attorney Kate Dyer, “Have you ever knowingly and willfully violated a pipeline safety regulation?”

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“No,” Arnett told the jury in the court of U.S. District Judge Thelton Henderson.

PG&E is accused of 12 counts of violating the federal Natural Gas Pipeline Safety Act and one count of obstructing a National Transportation Safety Board probe into a 2010 pipeline explosion in San Bruno that killed eight people.

The board concluded that the cause of the blast was a defectively welded pipe that was incorrectly listed as seamless in PG&E records.

The federal charges include failing to gather and integrate data on pipelines, failing to keep records of repairs, failing to assess and prioritize risks such as defects in the lines, and failing to maintain pressure-test records on pipelines.

The alleged violations concerns several Peninsula and East Bay high-pressure natural gas transmission lines, including Line 132, the pipeline that exploded in San Bruno.

Arnett began his testimony as a witness called by the prosecution on Wednesday and was cross-examined by Dyer Thursday on behalf of PG&E.

The attorney asked him to validate eight thick binders containing about 4,600 pages of reports on high-pressure water tests, known as hydrotests, on the lines.

Arnett said he had recently reviewed them in the offices of PG&E lawyers and agreed that they were PG&E business records. The reports were then entered into evidence.

PG&E attorneys gave prosecutors about 1,600 pages of the reports in February and another 3,000 last week.

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Outside the presence of the jury on Tuesday, Assistant U.S. Attorney Hallie Hoffman opposed allowing use of the new batch of 3,000 pages, saying that prosecutors had subpoenaed such records two years ago and that it was too late for PG&E to produce them. PG&E attorneys said they hadn’t known the additional records were wanted.

Henderson ruled on Wednesday morning that the records could be admitted as evidence.

During redirect examination Thursday, Hoffman gave jurors their first hint of the controversy by asking Arnett whether he knew the records were subpoenaed two years ago. He said he did not know.

The prosecutor then asked whether Arnett knew why PG&E provided the additional pages “only last week” and Arnett responded he did not know.

Hoffman then showed Arnett and the jury several examples of reports that appeared to be duplicates of one another or to be missing required information such as dates and exact locations. Arnett said he hadn’t noticed the discrepancies during his review.

One report seemed to go back and forth between two separate tests done on Line 132 in March and June 2011, and Arnett said he didn’t know why the document was prepared that way.

The trial continues tomorrow with testimony from PG&E pipeline corrosion control supervisor David Aguiar.

Henderson has ruled that because causing the San Bruno explosion is not an element of any of the 13 federal charges, prosecutors may not seek to link the alleged safety violations directly to the explosion.

If convicted of all the criminal charges, PG&E could face a fine of up to $562 million.

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In a separate civil proceeding, the California Public Utilities Commission fined PG&E $1.6 billion in 2015 for the San Bruno explosion and pipeline record-keeping and operation deficiencies.