A year on from her shock resignation as first minister, Nicola Sturgeon's legacy has been put under the microscope.

Ms Sturgeon stunned colleagues and opponents on February 15 2023 as she announced she would stand down from the top job during a hastily-prepared press conference at Bute House, the first minister's official residence in Edinburgh.

She was the country's longest serving first minister and the first woman to hold the post.

But 12 months later, amid investigations and inquiries, Ms Sturgeon's name remains at the forefront of the political landscape.

READ MORE: Can Yousaf calm the SNP storm a year on from Sturgeon exit?

In her resignation speech, Ms Sturgeon said she believed the "time is now", stating stepping aside was in the best interests of herself, the SNP and the country.

No obvious successor initially emerged and a bitter leadership contest was the first time the public had seen signs of infighting and turmoil taking place behind the scenes.

The Herald: Nicola Sturgeon speaking to reporters in June last year after she returned home following her arrest. Photo Getty.

The five-week contest eventually saw then health secretary Humza Yousaf selected to replace Ms Sturgeon.

But his first week in charge was overshadowed just days later by action from the police investigation Operation Branchform into the spending of £600,000 of SNP finances.

READ MORE: 'SNP's difficulties will get worse under Yousaf's weak leadership'

Ms Sturgeon's husband, Peter Murrell, who resigned as SNP chief executive during the leadership contest, was arrested and questioned for about 12 hours before being released without charge pending further investigation.

The image of the blue tent erected by officers in the couple's front garden in Glasgow was splashed over most national newspapers the following day.

Officers were seen searching a small garden shed and the party's Edinburgh headquarters were also searched.

The Herald: First Minister Humza Yousaf speaks with the media following the SNP a group meeting at the Scottish Parliament on June 13, 2023 in Edinburgh, Scotland. First Minister Humza Yousaf says he will not suspend Nicola Sturgeon from the SNP, following the former party leader being arrested and released without charge on Sunday as part of a police investigation into SNP finances. (Photo by Jeff J Mitchell/Getty Images).

The party's former treasurer, Colin Beattie, was arrested weeks later over the same probe but was also released without charge.

And in June, Ms Sturgeon was herself arrested, spending seven hours in custody before police released her without charge, with the Glasgow Southside MSP later telling journalists she was "certain" she had "done nothing wrong".

But the support Ms Sturgeon experienced from many of her party's own politicians and activists remained unwavering, as she received a standing ovation at the SNP conference in October 2023.

READ MORE: SNP MSP adds to demands for review of deal with Greens

Ms Sturgeon later denied her presence overshadowed Mr Yousaf's first conference in charge.

In recent weeks, Ms Sturgeon's legacy has again been called into question over her retention of informal messages received and sent during the UK Covid-19 Inquiry.

During her evidence to the inquiry's Edinburgh hearings, Ms Sturgeon confirmed she had deleted WhatsApp messages sent to officials during the pandemic, insisting it was in line with Scottish Government policy and key information had been retained on the official record.

The former first minister also became visibly emotional as she recounted the tough decisions taken during the pandemic, stating she would carry the regrets for "as long as I live".

Since her resignation, the SNP - and Scottish Government - have been battling with a resurgence of Labour, with both parties targeting the other's seats at the upcoming Westminster election.

The first electoral test without Ms Sturgeon at the helm came in the Rutherglen and Hamilton West by-election after a recall petition removed former SNP MP Margaret Ferrier following her coronavirus rule breaking.

Labour won the seat with a 20-point swing over the SNP.

That result has given the SNP's opponents hope amid an upcoming fight for the most Scottish seats at the forthcoming general election.

Polling shows the SNP's lead over Labour is narrowing, the Ipsos' Scottish Political Monitor showing the SNP remains seven points ahead, down from a 12-point lead in May, and a 10-point lead in November.

And Ms Sturgeon's key ambition of Scottish independence remains unrealised - with the SNP now going into the general election with the strategy of winning a majority of seats in Scotland to launch immediate negotiations.

Ms Sturgeon remains in Holyrood as an MSP and is now writing a "deeply personal" memoir on her life as she rose from a working class Ayrshire family to the steps of Bute House.

It is expected to be published in 2025.